Tamoxifen

updated

Tamoxifen is an FDA-approved medicine for breast cancer in women and men, with initial US approval in 1977 and a 13,388-woman prevention trial behind it. Sellers promote it for gynecomastia prevention and post-cycle recovery. In men starting bicalutamide it cut gynecomastia (pooled RR 0.18), and it raises LH, FSH and testosterone in healthy men, but a PubMed search on 9 October 2026 found no controlled trial of it for gynecomastia or hormonal recovery in steroid users.

Nonsteroidal antiestrogen

  • The SOLTAMOX label gives tamoxifen's initial US approval as 1977; openFDA lists SOLTAMOX approved on 29 October 2005 and generic tablets from 20 February 2003.
  • In NSABP P-1 (13,388 high-risk women), invasive breast cancer fell 44% (86 versus 156 cases) over a median 4.2 years, with no overall mortality difference.
  • In 282 men on bicalutamide, breast events at 6 months occurred in 8.8% on the highest tamoxifen dose versus 96.7% on placebo, and were common in all groups at 24 months after tamoxifen stopped.
  • A meta-analysis of 9 randomized trials in men on bicalutamide found tamoxifen lowered gynecomastia (RR 0.18, 95% CI 0.08 to 0.38).
  • The SOLTAMOX boxed warning covers uterine malignancies, stroke and pulmonary embolism, some fatal; the rates come from women.
  • A PubMed search on 9 October 2026 returned 31 records on tamoxifen with steroid or post-cycle terms; none was a controlled trial in steroid users.

What is tamoxifen approved to do?

Tamoxifen has been FDA-approved since 1977 and is labeled for breast cancer in women and men. Use for gynecomastia prevention or recovery after steroid cycles is not a labeled use.

The tamoxifen citrate tablet label says tamoxifen is effective for metastatic breast cancer in women and men. The SOLTAMOX label also describes use for adjuvant treatment, ductal carcinoma in situ and breast cancer risk reduction. The label versions used here took effect on 10 November 2025 (tablets) and 29 November 2021 (SOLTAMOX).

The SOLTAMOX label gives tamoxifen's initial US approval as 1977. openFDA lists SOLTAMOX under NDA 021807, approved 29 October 2005, and generic tamoxifen citrate tablets under ANDAs approved from 20 February 2003 (for example ANDA 074732, Mylan). A query for the original NOLVADEX brand returned no openFDA record, so the 1977 year rests on the SOLTAMOX label. Approvals outside the United States are not covered here.

Tamoxifen base is C26H29NO (371.5 g/mol, CAS 10540-29-1, PubChem CID 2733526), described by the label as the trans isomer of a triphenylethylene derivative. The salt in US tablets is tamoxifen citrate (C32H37NO8, 563.6 g/mol, CAS 54965-24-1, CID 2733525). Label doses are expressed as tamoxifen.

Tamoxifen tablet label, version effective 10 November 2025: male data, mechanism, PK

FDA prescribing information

DailyMed, U.S. National Library of Medicine. Tamoxifen citrate oral tablets, prescribing information, label version effective 10 November 2025. Set ID c82205a3-ae0c-4ce5-b04b-9581cd8c70d4.

The label says tamoxifen is effective for metastatic breast cancer in women and men; published results in 132 evaluable men with breast cancer showed a 50% objective response rate (66 responders). Its male safety text says literature and case reports suggest a safety profile in men similar to that in women, that loss of libido and impotence have led men to stop tamoxifen, and that in oligospermic men treated with tamoxifen, LH, FSH, testosterone and estrogen levels were elevated with no significant clinical changes reported. Tamoxifen is described as a nonsteroidal antiestrogen that competes with estradiol for estrogen receptor binding in tissues such as breast. After a single dose, plasma levels peaked at about 40 ng/mL about 5 hours later, and the terminal elimination half-life is about 5 to 7 days.

Participants / model
Women and men with breast cancer; oligospermic men (safety section); PK participants
Treatment
Tamoxifen citrate oral tablets
Follow-up
Label version effective 10 November 2025
Study design
FDA prescribing information
Funding
not stated in the source

The male statements come from literature and case reports summarized in the label, not from a labeled trial in men without cancer.

Read the original source
SOLTAMOX label, version effective 29 November 2021: 1977 approval, boxed warning, P-1

FDA prescribing information

DailyMed, U.S. National Library of Medicine. SOLTAMOX (tamoxifen citrate) oral solution, prescribing information, label version effective 29 November 2021. Set ID 1e6ff055-590c-41e6-9530-1fdf04cdbd02.

The label gives tamoxifen's initial US approval as 1977 and carries a boxed warning for uterine malignancies, stroke and pulmonary embolism, some fatal. Rates per 1,000 women-years in the NSABP P-1 prevention trial, tamoxifen versus placebo, were 2.20 versus 0.71 for endometrial adenocarcinoma, 0.17 versus 0.04 for uterine sarcoma, 1.43 versus 1.00 for stroke and 0.75 versus 0.25 for pulmonary embolism. In P-1, 13,388 women at high risk were randomized to tamoxifen or placebo for 5 years; after a median 4.2 years, invasive breast cancer fell 44% (86 versus 156 cases; RR 0.56, 95% CI 0.43 to 0.72), with no overall mortality difference.

Participants / model
Adults with breast cancer; women with ductal carcinoma in situ or at high risk (P-1)
Treatment
SOLTAMOX oral solution; P-1 used another tamoxifen formulation
Follow-up
Label version effective 29 November 2021; P-1 median follow-up 4.2 years
Study design
FDA prescribing information
Funding
not stated in the source

The boxed-warning rates are from women; no male thromboembolism or stroke rate was found. The uterine sarcoma placebo rate is taken as 0.04 per 1,000 women-years, the figure consistent with the boxed warning.

Read the original source
Drugs@FDA: SOLTAMOX approved 29 October 2005, generic tablets from 20 February 2003

Regulatory record

U.S. Food and Drug Administration. Drugs@FDA application record for NDA 021807 (SOLTAMOX), with generic tamoxifen citrate tablet applications such as ANDA 074732. Dates read from the openFDA Drugs@FDA records.

openFDA lists SOLTAMOX under NDA 021807, approved 29 October 2005, and generic tamoxifen citrate tablets under ANDAs approved from 20 February 2003 (for example ANDA 074732, Mylan). A query for the original NOLVADEX brand returned no openFDA record, so the 1977 year rests on the SOLTAMOX label.

Participants / model
Not a clinical population
Treatment
Drug applications
Follow-up
Approvals from 2003 to 2005
Study design
FDA application records
Funding
not stated in the source

These records give approval dates for the oral solution and generic tablets. The original 1977 approval is not in the openFDA record.

Read the original source
PubChem: tamoxifen and tamoxifen citrate identity

Chemical identity record

National Library of Medicine. PubChem compound records CID 2733526 (tamoxifen) and CID 2733525 (tamoxifen citrate).

Tamoxifen base: PubChem CID 2733526, C26H29NO, 371.5 g/mol, CAS 10540-29-1; the label describes it as the trans isomer of a triphenylethylene derivative. Tamoxifen citrate, the salt in US tablets: CID 2733525, C32H37NO8, 563.6 g/mol, CAS 54965-24-1. Label doses are expressed as tamoxifen, not the citrate salt.

Participants / model
Chemical identity, not a clinical population
Treatment
Defined molecule and salt
Follow-up
Not applicable
Study design
NLM chemical record
Funding
not stated in the source

Identity record only; it says nothing about efficacy or safety. Salt and base masses differ, so they are not interchangeable.

Read the original source

What did the breast cancer prevention trial and male breast cancer data find?

In NSABP P-1, 13,388 high-risk women given tamoxifen or placebo for 5 years had 44% fewer invasive breast cancers over a median 4.2 years, with no overall mortality difference. In 132 evaluable men with breast cancer, 50% had an objective response.

In NSABP P-1, 13,388 women at high risk were randomized to tamoxifen 20 mg a day or placebo for 5 years. After a median 4.2 years, invasive breast cancer fell 44% (86 versus 156 cases; RR 0.56, 95% CI 0.43 to 0.72), with no overall mortality difference.

The tablet label says tamoxifen is effective for metastatic breast cancer in women and men; published results in 132 evaluable men with breast cancer showed a 50% objective response rate (66 responders). These are results in people with breast cancer or at high risk of it. They do not describe men without cancer.

SOLTAMOX label, version effective 29 November 2021: 1977 approval, boxed warning, P-1

FDA prescribing information

DailyMed, U.S. National Library of Medicine. SOLTAMOX (tamoxifen citrate) oral solution, prescribing information, label version effective 29 November 2021. Set ID 1e6ff055-590c-41e6-9530-1fdf04cdbd02.

The label gives tamoxifen's initial US approval as 1977 and carries a boxed warning for uterine malignancies, stroke and pulmonary embolism, some fatal. Rates per 1,000 women-years in the NSABP P-1 prevention trial, tamoxifen versus placebo, were 2.20 versus 0.71 for endometrial adenocarcinoma, 0.17 versus 0.04 for uterine sarcoma, 1.43 versus 1.00 for stroke and 0.75 versus 0.25 for pulmonary embolism. In P-1, 13,388 women at high risk were randomized to tamoxifen or placebo for 5 years; after a median 4.2 years, invasive breast cancer fell 44% (86 versus 156 cases; RR 0.56, 95% CI 0.43 to 0.72), with no overall mortality difference.

Participants / model
Adults with breast cancer; women with ductal carcinoma in situ or at high risk (P-1)
Treatment
SOLTAMOX oral solution; P-1 used another tamoxifen formulation
Follow-up
Label version effective 29 November 2021; P-1 median follow-up 4.2 years
Study design
FDA prescribing information
Funding
not stated in the source

The boxed-warning rates are from women; no male thromboembolism or stroke rate was found. The uterine sarcoma placebo rate is taken as 0.04 per 1,000 women-years, the figure consistent with the boxed warning.

Read the original source
Tamoxifen tablet label, version effective 10 November 2025: male data, mechanism, PK

FDA prescribing information

DailyMed, U.S. National Library of Medicine. Tamoxifen citrate oral tablets, prescribing information, label version effective 10 November 2025. Set ID c82205a3-ae0c-4ce5-b04b-9581cd8c70d4.

The label says tamoxifen is effective for metastatic breast cancer in women and men; published results in 132 evaluable men with breast cancer showed a 50% objective response rate (66 responders). Its male safety text says literature and case reports suggest a safety profile in men similar to that in women, that loss of libido and impotence have led men to stop tamoxifen, and that in oligospermic men treated with tamoxifen, LH, FSH, testosterone and estrogen levels were elevated with no significant clinical changes reported. Tamoxifen is described as a nonsteroidal antiestrogen that competes with estradiol for estrogen receptor binding in tissues such as breast. After a single dose, plasma levels peaked at about 40 ng/mL about 5 hours later, and the terminal elimination half-life is about 5 to 7 days.

Participants / model
Women and men with breast cancer; oligospermic men (safety section); PK participants
Treatment
Tamoxifen citrate oral tablets
Follow-up
Label version effective 10 November 2025
Study design
FDA prescribing information
Funding
not stated in the source

The male statements come from literature and case reports summarized in the label, not from a labeled trial in men without cancer.

Read the original source

Does tamoxifen treat or prevent gynecomastia?

Partly, in the settings tested. In men starting bicalutamide, tamoxifen cut gynecomastia (pooled RR 0.18) and breast events in a dose-dependent way, but breast events were common again after it stopped. A European guideline recommends against SERMs for gynecomastia in general.

In a double-blind crossover trial in 10 men with gynecomastia, one-month courses of tamoxifen 10 mg twice daily and placebo were given in random order. Breast size decreased on tamoxifen in 7 of 10 (P < 0.005), placebo had no effect, and all 4 men with painful gynecomastia had relief. The reduction was partial: at 9 to 12 months of follow-up in 8 men, one responder had tenderness return and one nonresponder grew.

In a prospective single-arm cohort of 81 men (mean age 42.8) with idiopathic gynecomastia treated with tamoxifen 10 mg a day at one UK breast clinic from 2004 to 2015, 90.1% (73) had complete resolution, and 2 of the 8 non-responders had surgery. There was no control group, so spontaneous regression cannot be separated from a drug effect.

In 282 men with prostate cancer on bicalutamide 150 mg a day, tamoxifen for 12 months cut breast events (gynecomastia, breast pain or both) by dose: at 6 months they occurred in 86.2%, 60.0%, 55.3%, 23.5% and 8.8% of men on 1, 2.5, 5, 10 and 20 mg, versus 96.7% on placebo. After tamoxifen stopped and bicalutamide continued for another 12 months, breast events were common in all groups at 24 months, so this trial does not show a lasting protective effect. Hot flushes rose at 5 mg or more.

A meta-analysis of 9 randomized trials in men on bicalutamide found that tamoxifen lowered the risk of gynecomastia (RR 0.18, 95% CI 0.08 to 0.38) and breast pain (RR 0.18, 95% CI 0.07 to 0.43), more than radiotherapy (gynecomastia RR 0.48, 95% CI 0.38 to 0.59), while anastrozole showed no significant benefit.

The European Academy of Andrology guideline recommends against using SERMs, aromatase inhibitors or non-aromatizable androgens to treat gynecomastia in general (strong recommendation, low-quality evidence), recommends watchful waiting after a causative substance is stopped, and reserves surgery for long-lasting gynecomastia. It addresses treatment of gynecomastia, not prevention during antiandrogen therapy.

10 men, 1 month each: breast size down in 7 of 10

Randomized controlled trial

Parker LN et al. Metabolism. 1986;35(8):705-8. PMID 3526085.

Breast size decreased on tamoxifen in 7 of 10 men (P < 0.005), placebo had no effect, and all 4 men with painful gynecomastia had relief. The reduction was partial; at 9 to 12 months of follow-up in 8 men, one responder had tenderness return and one nonresponder grew.

Participants / model
10 men with benign gynecomastia
Treatment
Oral tamoxifen 10 mg twice daily or placebo, in random order
Follow-up
1 month per course
Study design
Double-blind randomized crossover trial
Funding
not stated in the source

Very small trial with a partial response.

Read the original source
81 men, uncontrolled cohort: 90.1% complete resolution

Human study

Mannu GS et al. Breast J. 2018;24(6):1043-1045. PMID 30079473.

90.1% (73 of 81) had complete resolution, and 2 of the 8 non-responders had surgery.

Participants / model
81 men (mean age 42.8) with primary (idiopathic) gynecomastia, 87.7% with breast pain
Treatment
Oral tamoxifen 10 mg daily
Follow-up
One UK breast clinic, 2004 to 2015
Study design
Prospective cohort study, uncontrolled
Funding
not stated in the source

There was no control group, so spontaneous regression cannot be separated from a drug effect.

Read the original source
282 men on bicalutamide: breast events 96.7% on placebo to 8.8% at the top dose

Randomized controlled trial

Fradet Y et al. Eur Urol. 2007;52(1):106-14. PMID 17270340.

At 6 months, breast events (gynecomastia, breast pain or both) occurred in 86.2%, 60.0%, 55.3%, 23.5% and 8.8% of men on tamoxifen 1, 2.5, 5, 10 and 20 mg, versus 96.7% on placebo. After tamoxifen stopped and bicalutamide continued for another 12 months, breast events were common in all groups at 24 months. Hot flushes rose at 5 mg or more.

Participants / model
282 men with prostate cancer on bicalutamide monotherapy
Treatment
Oral tamoxifen 1 to 20 mg daily or placebo, with bicalutamide 150 mg daily
Follow-up
12 months of tamoxifen, followed to 24 months
Study design
Randomized dose-response trial
Funding
not stated in the source

This is antiandrogen-induced gynecomastia, not gynecomastia from anabolic steroids. The protection did not last after tamoxifen stopped.

Read the original source
Meta-analysis of 9 randomized trials: tamoxifen RR 0.18 for gynecomastia

Systematic review and meta-analysis

Spagnolo L et al. J Endocrinol Invest. 2025;48(7):1659-1668. PMID 40244528.

Tamoxifen lowered the risk of gynecomastia (RR 0.18, 95% CI 0.08 to 0.38) and breast pain (RR 0.18, 95% CI 0.07 to 0.43), more than radiotherapy (gynecomastia RR 0.48, 95% CI 0.38 to 0.59), while anastrozole showed no significant benefit.

Participants / model
Men with prostate cancer on bicalutamide, 9 randomized trials
Treatment
Oral tamoxifen, oral anastrozole or breast radiotherapy versus bicalutamide alone or with placebo or sham
Follow-up
Pooled randomized trials
Study design
Systematic review and meta-analysis of 9 randomized trials
Funding
not stated in the source

Applies to men on bicalutamide.

Read the original source
European Academy of Andrology guideline: no SERMs or aromatase inhibitors for gynecomastia in general

Human study

Kanakis GA et al. Andrology. 2019;7(6):778-793. PMID 31099174.

The guideline recommends against using SERMs, aromatase inhibitors or non-aromatizable androgens to treat gynecomastia in general (strong recommendation, low-quality evidence), recommends watchful waiting after a causative substance is stopped, and reserves surgery for long-lasting gynecomastia.

Participants / model
Boys and men with gynecomastia (guideline scope)
Treatment
Not drug-specific
Follow-up
Not applicable
Study design
Clinical practice guideline (GRADE)
Funding
not stated in the source

It addresses treatment of gynecomastia, not prevention during antiandrogen therapy.

Read the original source

What does tamoxifen do to hormones in men?

In healthy men, tamoxifen raised LH, FSH, testosterone and estradiol, and in a 2-week crossover it raised LH, FSH and testosterone more than raloxifene did. In men with idiopathic oligospermia, sperm density improved only in men below 20 million/mL with normal baseline FSH.

In normal men, tamoxifen 20 mg a day for 10 days produced a moderate increase in LH, FSH, testosterone and estradiol, comparable to clomiphene 150 mg, and 6 weeks of tamoxifen increased the LH response to LHRH. The abstract does not give subject numbers.

In a randomized open-label crossover in 10 healthy men, 2 weeks each of tamoxifen (10 and 20 mg a day) and raloxifene (60 and 120 mg a day) both raised LH, FSH and testosterone, with larger mean rises on tamoxifen (testosterone 40% versus 25%; LH 70% versus 30%). At the higher dose tamoxifen also lowered IGF-I by 25% and raised SHBG by 20%.

In men with idiopathic oligospermia treated for 6 to 9 months, gonadotropins, testosterone and estradiol rose, but sperm density improved only in men below 20 million/mL with normal baseline FSH. The tablet label likewise says LH, FSH, testosterone and estrogen levels were elevated in oligospermic men, with no significant clinical changes reported.

Normal men and oligospermic men: LH, FSH, testosterone, estradiol up

Human study

Vermeulen A et al. Fertil Steril. 1978;29(3):320-7. PMID 640052.

In normal men, tamoxifen produced a moderate increase in LH, FSH, testosterone and estradiol, comparable to clomiphene 150 mg, and 6 weeks of tamoxifen increased the LH response to LHRH. In men with idiopathic oligospermia treated for 6 to 9 months, gonadotropins, testosterone and estradiol rose, but sperm density improved only in men below 20 million/mL with normal baseline FSH. Subject numbers are not given in the abstract.

Participants / model
Normal men; men with idiopathic oligospermia
Treatment
Oral tamoxifen 20 mg daily
Follow-up
10 days to 9 months
Study design
Clinical study
Funding
not stated in the source

Subject numbers are not given in the abstract.

Read the original source
10 healthy men, 2 weeks each: tamoxifen raised LH 70% and testosterone 40%

Randomized controlled trial

Birzniece V et al. J Clin Endocrinol Metab. 2010;95(12):5443-8. PMID 20843951.

Tamoxifen and raloxifene both raised LH, FSH and testosterone, with larger mean rises on tamoxifen (testosterone 40% versus 25%; LH 70% versus 30%). At the higher dose tamoxifen also lowered IGF-I by 25% and raised SHBG by 20%.

Participants / model
10 healthy men
Treatment
Oral tamoxifen 10 and 20 mg daily and raloxifene 60 and 120 mg daily
Follow-up
2 weeks per drug
Study design
Randomized open-label crossover study
Funding
not stated in the source

Short hormone study in healthy men.

Read the original source
Tamoxifen tablet label, version effective 10 November 2025: male data, mechanism, PK

FDA prescribing information

DailyMed, U.S. National Library of Medicine. Tamoxifen citrate oral tablets, prescribing information, label version effective 10 November 2025. Set ID c82205a3-ae0c-4ce5-b04b-9581cd8c70d4.

The label says tamoxifen is effective for metastatic breast cancer in women and men; published results in 132 evaluable men with breast cancer showed a 50% objective response rate (66 responders). Its male safety text says literature and case reports suggest a safety profile in men similar to that in women, that loss of libido and impotence have led men to stop tamoxifen, and that in oligospermic men treated with tamoxifen, LH, FSH, testosterone and estrogen levels were elevated with no significant clinical changes reported. Tamoxifen is described as a nonsteroidal antiestrogen that competes with estradiol for estrogen receptor binding in tissues such as breast. After a single dose, plasma levels peaked at about 40 ng/mL about 5 hours later, and the terminal elimination half-life is about 5 to 7 days.

Participants / model
Women and men with breast cancer; oligospermic men (safety section); PK participants
Treatment
Tamoxifen citrate oral tablets
Follow-up
Label version effective 10 November 2025
Study design
FDA prescribing information
Funding
not stated in the source

The male statements come from literature and case reports summarized in the label, not from a labeled trial in men without cancer.

Read the original source

Is tamoxifen the standard for gynecomastia prevention and post-cycle therapy?

Partly. Prevention of antiandrogen-induced gynecomastia and the rise in LH and FSH are documented. A PubMed search on 9 October 2026 found no controlled trial of tamoxifen for gynecomastia or hormonal recovery in anabolic steroid users.

Sellers describe tamoxifen as the standard for gynecomastia prevention and post-cycle therapy because it blocks estrogen receptors in the breast and restores LH and FSH by blocking hypothalamic estrogen receptors. The breast-tissue and LH and FSH parts are documented in the studies above. Use alongside anabolic steroids, gynecomastia from anabolic steroids, and post-cycle recovery are the parts with no controlled trial.

A PubMed search on 9 October 2026 for tamoxifen with anabolic steroid, bodybuilding or post-cycle terms returned 31 records: reviews, case reports and case series (including an uncontrolled Spanish clinic series in which men whose sperm production had not recovered 6 months after stopping anabolic steroids were given tamoxifen 20 mg a day, with unpredictable response), surveys, drug-detection and seized-product analyses, a forum analysis, an internet search-interest analysis, a breast cancer treatment report in elderly patients, and animal or in-vitro studies. None was a controlled trial of tamoxifen for gynecomastia or hormonal recovery in anabolic steroid users.

A review of anabolic steroid-induced hypogonadism was planned as a meta-analysis, but no quality studies met its inclusion criteria; its management advice (judicious testosterone, hCG and SERMs) rests on published literature and expert opinion.

The most direct post-cycle comparison found is a retrospective two-center cohort of 79 recreational male steroid users who stopped after 6 months or less of use and had normal pre-cycle hormones and semen. Expectant monitoring was compared with clomiphene and with clomiphene plus hCG. Both drug regimens sped hormonal recovery, but hormones normalized in all groups by month 6, and normozoospermia at 12 months was 87.5%, 69.2% and 58.6% with clomiphene plus hCG, clomiphene and no treatment. Tamoxifen was not studied.

PubMed search, 9 October 2026: 31 records, no controlled trial in steroid users

PubMed search record

PubMed search run on 9 October 2026: tamoxifen[tiab] AND (anabolic steroid*[tiab] OR anabolic-androgenic[tiab] OR anabolic androgenic[tiab] OR bodybuild*[tiab] OR post-cycle[tiab] OR "post cycle"[tiab]). 31 records returned.

The search returned 31 records: reviews (including the hypogonadism review on this page), case reports and case series (including an uncontrolled Spanish clinic series in which men whose sperm production had not recovered 6 months after stopping anabolic steroids were given tamoxifen 20 mg a day, with unpredictable response), surveys, drug-detection and seized-product analyses, a forum analysis, an internet search-interest analysis, a breast cancer treatment report in elderly patients, and animal or in-vitro studies. None was a controlled trial of tamoxifen for gynecomastia or hormonal recovery in anabolic steroid users.

Participants / model
Records returned, not a population
Treatment
Not applicable
Follow-up
Search run on 9 October 2026
Study design
Literature search
Funding
not stated in the source

A search result shows what PubMed returned on that date. It is not proof that no unindexed study exists.

Read the original source
Review of AAS-induced hypogonadism: no quality studies met inclusion criteria

Human study

Rahnema CD et al. Fertil Steril. 2014;101(5):1271-9. PMID 24636400.

A review of anabolic steroid-induced hypogonadism was planned as a meta-analysis, but no quality studies met its inclusion criteria. Its management advice (judicious testosterone, hCG and SERMs) rests on published literature and expert opinion.

Participants / model
Men with symptomatic hypogonadism after nonprescribed anabolic steroid use
Treatment
Not drug-specific
Follow-up
Not applicable
Study design
Review; meta-analysis not possible
Funding
not stated in the source

The review shows how little controlled evidence existed for recovery treatment, not that a treatment works.

Read the original source
79 men after short steroid cycles: recovery with clomiphene, with or without hCG, versus none

Human study

İbis MA et al. BJU Int. 2026;137(1):154-165. PMID 41147237.

Both drug regimens sped hormonal recovery, but hormones normalized in all groups by month 6. Normozoospermia at 12 months was 87.5%, 69.2% and 58.6% with clomiphene plus hCG, clomiphene and no treatment.

Participants / model
79 recreational male anabolic steroid users who stopped after 6 months or less of use, with normal pre-cycle hormones and semen
Treatment
Expectant monitoring, clomiphene, or clomiphene plus hCG
Follow-up
Followed to 12 months
Study design
Retrospective two-center cohort study
Funding
not stated in the source

Tamoxifen was not studied. This is the most direct post-cycle comparison found, and it was not randomized.

Read the original source

How does tamoxifen work, and what does the body do with it?

Tamoxifen is a nonsteroidal antiestrogen that competes with estradiol for estrogen receptor binding in tissues such as breast. After a single dose, plasma levels peaked at about 40 ng/mL about 5 hours later, and the terminal elimination half-life is about 5 to 7 days.

The tablet label describes tamoxifen as a nonsteroidal antiestrogen that competes with estradiol for estrogen receptor binding in tissues such as breast. In healthy men and oligospermic men the measured hormonal result was a rise in LH, FSH, testosterone and estradiol.

After a single dose, plasma levels peaked at about 40 ng/mL about 5 hours later, and the terminal elimination half-life is about 5 to 7 days.

Tamoxifen tablet label, version effective 10 November 2025: male data, mechanism, PK

FDA prescribing information

DailyMed, U.S. National Library of Medicine. Tamoxifen citrate oral tablets, prescribing information, label version effective 10 November 2025. Set ID c82205a3-ae0c-4ce5-b04b-9581cd8c70d4.

The label says tamoxifen is effective for metastatic breast cancer in women and men; published results in 132 evaluable men with breast cancer showed a 50% objective response rate (66 responders). Its male safety text says literature and case reports suggest a safety profile in men similar to that in women, that loss of libido and impotence have led men to stop tamoxifen, and that in oligospermic men treated with tamoxifen, LH, FSH, testosterone and estrogen levels were elevated with no significant clinical changes reported. Tamoxifen is described as a nonsteroidal antiestrogen that competes with estradiol for estrogen receptor binding in tissues such as breast. After a single dose, plasma levels peaked at about 40 ng/mL about 5 hours later, and the terminal elimination half-life is about 5 to 7 days.

Participants / model
Women and men with breast cancer; oligospermic men (safety section); PK participants
Treatment
Tamoxifen citrate oral tablets
Follow-up
Label version effective 10 November 2025
Study design
FDA prescribing information
Funding
not stated in the source

The male statements come from literature and case reports summarized in the label, not from a labeled trial in men without cancer.

Read the original source
Normal men and oligospermic men: LH, FSH, testosterone, estradiol up

Human study

Vermeulen A et al. Fertil Steril. 1978;29(3):320-7. PMID 640052.

In normal men, tamoxifen produced a moderate increase in LH, FSH, testosterone and estradiol, comparable to clomiphene 150 mg, and 6 weeks of tamoxifen increased the LH response to LHRH. In men with idiopathic oligospermia treated for 6 to 9 months, gonadotropins, testosterone and estradiol rose, but sperm density improved only in men below 20 million/mL with normal baseline FSH. Subject numbers are not given in the abstract.

Participants / model
Normal men; men with idiopathic oligospermia
Treatment
Oral tamoxifen 20 mg daily
Follow-up
10 days to 9 months
Study design
Clinical study
Funding
not stated in the source

Subject numbers are not given in the abstract.

Read the original source

What risks do the labels and male studies report?

The SOLTAMOX label carries a boxed warning for uterine malignancies, stroke and pulmonary embolism, some fatal. Those rates come from women. In men, the label cites loss of libido and impotence as reasons for stopping, and reviews found fewer than 5% withdrawing for toxicity.

Rates per 1,000 women-years in the NSABP P-1 prevention trial, tamoxifen versus placebo, were 2.20 versus 0.71 for endometrial adenocarcinoma, 0.17 versus 0.04 for uterine sarcoma, 1.43 versus 1.00 for stroke and 0.75 versus 0.25 for pulmonary embolism. These are rates in women. No male thromboembolism or stroke rate was found.

The tablet label's male safety text says literature and case reports suggest a safety profile in men similar to that in women, and that loss of libido and impotence have led men to stop tamoxifen. A review of adverse events in tamoxifen-treated men (prostate cancer, breast cancer, infertility, idiopathic gynecomastia) found the profile varied by population: few adverse events in men treated for infertility or idiopathic gynecomastia, more in men with prostate or breast cancer, and fewer than 5% withdrawing for toxicity, most of them male breast cancer patients stopping for cardiovascular events. The authors note that long-term studies documenting side effects in men are lacking.

In the 282-man bicalutamide trial, hot flushes rose at 5 mg or more. In the 10-man crossover, tamoxifen at the higher dose lowered IGF-I by 25% and raised SHBG by 20%.

SOLTAMOX label, version effective 29 November 2021: 1977 approval, boxed warning, P-1

FDA prescribing information

DailyMed, U.S. National Library of Medicine. SOLTAMOX (tamoxifen citrate) oral solution, prescribing information, label version effective 29 November 2021. Set ID 1e6ff055-590c-41e6-9530-1fdf04cdbd02.

The label gives tamoxifen's initial US approval as 1977 and carries a boxed warning for uterine malignancies, stroke and pulmonary embolism, some fatal. Rates per 1,000 women-years in the NSABP P-1 prevention trial, tamoxifen versus placebo, were 2.20 versus 0.71 for endometrial adenocarcinoma, 0.17 versus 0.04 for uterine sarcoma, 1.43 versus 1.00 for stroke and 0.75 versus 0.25 for pulmonary embolism. In P-1, 13,388 women at high risk were randomized to tamoxifen or placebo for 5 years; after a median 4.2 years, invasive breast cancer fell 44% (86 versus 156 cases; RR 0.56, 95% CI 0.43 to 0.72), with no overall mortality difference.

Participants / model
Adults with breast cancer; women with ductal carcinoma in situ or at high risk (P-1)
Treatment
SOLTAMOX oral solution; P-1 used another tamoxifen formulation
Follow-up
Label version effective 29 November 2021; P-1 median follow-up 4.2 years
Study design
FDA prescribing information
Funding
not stated in the source

The boxed-warning rates are from women; no male thromboembolism or stroke rate was found. The uterine sarcoma placebo rate is taken as 0.04 per 1,000 women-years, the figure consistent with the boxed warning.

Read the original source
Tamoxifen tablet label, version effective 10 November 2025: male data, mechanism, PK

FDA prescribing information

DailyMed, U.S. National Library of Medicine. Tamoxifen citrate oral tablets, prescribing information, label version effective 10 November 2025. Set ID c82205a3-ae0c-4ce5-b04b-9581cd8c70d4.

The label says tamoxifen is effective for metastatic breast cancer in women and men; published results in 132 evaluable men with breast cancer showed a 50% objective response rate (66 responders). Its male safety text says literature and case reports suggest a safety profile in men similar to that in women, that loss of libido and impotence have led men to stop tamoxifen, and that in oligospermic men treated with tamoxifen, LH, FSH, testosterone and estrogen levels were elevated with no significant clinical changes reported. Tamoxifen is described as a nonsteroidal antiestrogen that competes with estradiol for estrogen receptor binding in tissues such as breast. After a single dose, plasma levels peaked at about 40 ng/mL about 5 hours later, and the terminal elimination half-life is about 5 to 7 days.

Participants / model
Women and men with breast cancer; oligospermic men (safety section); PK participants
Treatment
Tamoxifen citrate oral tablets
Follow-up
Label version effective 10 November 2025
Study design
FDA prescribing information
Funding
not stated in the source

The male statements come from literature and case reports summarized in the label, not from a labeled trial in men without cancer.

Read the original source
Review of tamoxifen adverse events in men: varied by population, fewer than 5% withdrew

Human study

Wibowo E et al. Andrology. 2016;4(5):776-88. PMID 27152880.

The adverse-event profile varied by population: few adverse events in men treated for infertility or idiopathic gynecomastia, more in men with prostate or breast cancer, and fewer than 5% withdrawing for toxicity, most of them male breast cancer patients stopping for cardiovascular events. The authors note that long-term studies documenting side effects in men are lacking.

Participants / model
Men in published randomized and non-randomized tamoxifen studies (prostate cancer, breast cancer, infertility, idiopathic gynecomastia)
Treatment
Oral tamoxifen, various doses
Follow-up
Not applicable
Study design
Review of adverse events
Funding
not stated in the source

Long-term studies documenting side effects in men are lacking.

Read the original source
282 men on bicalutamide: breast events 96.7% on placebo to 8.8% at the top dose

Randomized controlled trial

Fradet Y et al. Eur Urol. 2007;52(1):106-14. PMID 17270340.

At 6 months, breast events (gynecomastia, breast pain or both) occurred in 86.2%, 60.0%, 55.3%, 23.5% and 8.8% of men on tamoxifen 1, 2.5, 5, 10 and 20 mg, versus 96.7% on placebo. After tamoxifen stopped and bicalutamide continued for another 12 months, breast events were common in all groups at 24 months. Hot flushes rose at 5 mg or more.

Participants / model
282 men with prostate cancer on bicalutamide monotherapy
Treatment
Oral tamoxifen 1 to 20 mg daily or placebo, with bicalutamide 150 mg daily
Follow-up
12 months of tamoxifen, followed to 24 months
Study design
Randomized dose-response trial
Funding
not stated in the source

This is antiandrogen-induced gynecomastia, not gynecomastia from anabolic steroids. The protection did not last after tamoxifen stopped.

Read the original source
10 healthy men, 2 weeks each: tamoxifen raised LH 70% and testosterone 40%

Randomized controlled trial

Birzniece V et al. J Clin Endocrinol Metab. 2010;95(12):5443-8. PMID 20843951.

Tamoxifen and raloxifene both raised LH, FSH and testosterone, with larger mean rises on tamoxifen (testosterone 40% versus 25%; LH 70% versus 30%). At the higher dose tamoxifen also lowered IGF-I by 25% and raised SHBG by 20%.

Participants / model
10 healthy men
Treatment
Oral tamoxifen 10 and 20 mg daily and raloxifene 60 and 120 mg daily
Follow-up
2 weeks per drug
Study design
Randomized open-label crossover study
Funding
not stated in the source

Short hormone study in healthy men.

Read the original source

Why does tamoxifen sit in A tier?

The A rests on an FDA approval since 1977 and very large randomized trials in women. In men there is randomized support for preventing antiandrogen-induced gynecomastia, but none found for gynecomastia from steroids or for post-cycle recovery.

The A applies to the approved breast cancer uses, backed by the 13,388-woman P-1 trial and decades of use. It also has randomized evidence in men for part of the supplier claim: in men starting bicalutamide, tamoxifen cut gynecomastia (pooled RR 0.18), and it raises LH, FSH and testosterone in healthy men.

The rest of the claim has no controlled trial behind it in the records found. Use alongside anabolic steroids, gynecomastia from anabolic steroids and post-cycle recovery had no controlled trial in the PubMed search run on 9 October 2026, and breast events returned after tamoxifen stopped in the bicalutamide dose-response trial.

SOLTAMOX label, version effective 29 November 2021: 1977 approval, boxed warning, P-1

FDA prescribing information

DailyMed, U.S. National Library of Medicine. SOLTAMOX (tamoxifen citrate) oral solution, prescribing information, label version effective 29 November 2021. Set ID 1e6ff055-590c-41e6-9530-1fdf04cdbd02.

The label gives tamoxifen's initial US approval as 1977 and carries a boxed warning for uterine malignancies, stroke and pulmonary embolism, some fatal. Rates per 1,000 women-years in the NSABP P-1 prevention trial, tamoxifen versus placebo, were 2.20 versus 0.71 for endometrial adenocarcinoma, 0.17 versus 0.04 for uterine sarcoma, 1.43 versus 1.00 for stroke and 0.75 versus 0.25 for pulmonary embolism. In P-1, 13,388 women at high risk were randomized to tamoxifen or placebo for 5 years; after a median 4.2 years, invasive breast cancer fell 44% (86 versus 156 cases; RR 0.56, 95% CI 0.43 to 0.72), with no overall mortality difference.

Participants / model
Adults with breast cancer; women with ductal carcinoma in situ or at high risk (P-1)
Treatment
SOLTAMOX oral solution; P-1 used another tamoxifen formulation
Follow-up
Label version effective 29 November 2021; P-1 median follow-up 4.2 years
Study design
FDA prescribing information
Funding
not stated in the source

The boxed-warning rates are from women; no male thromboembolism or stroke rate was found. The uterine sarcoma placebo rate is taken as 0.04 per 1,000 women-years, the figure consistent with the boxed warning.

Read the original source
Tamoxifen tablet label, version effective 10 November 2025: male data, mechanism, PK

FDA prescribing information

DailyMed, U.S. National Library of Medicine. Tamoxifen citrate oral tablets, prescribing information, label version effective 10 November 2025. Set ID c82205a3-ae0c-4ce5-b04b-9581cd8c70d4.

The label says tamoxifen is effective for metastatic breast cancer in women and men; published results in 132 evaluable men with breast cancer showed a 50% objective response rate (66 responders). Its male safety text says literature and case reports suggest a safety profile in men similar to that in women, that loss of libido and impotence have led men to stop tamoxifen, and that in oligospermic men treated with tamoxifen, LH, FSH, testosterone and estrogen levels were elevated with no significant clinical changes reported. Tamoxifen is described as a nonsteroidal antiestrogen that competes with estradiol for estrogen receptor binding in tissues such as breast. After a single dose, plasma levels peaked at about 40 ng/mL about 5 hours later, and the terminal elimination half-life is about 5 to 7 days.

Participants / model
Women and men with breast cancer; oligospermic men (safety section); PK participants
Treatment
Tamoxifen citrate oral tablets
Follow-up
Label version effective 10 November 2025
Study design
FDA prescribing information
Funding
not stated in the source

The male statements come from literature and case reports summarized in the label, not from a labeled trial in men without cancer.

Read the original source
282 men on bicalutamide: breast events 96.7% on placebo to 8.8% at the top dose

Randomized controlled trial

Fradet Y et al. Eur Urol. 2007;52(1):106-14. PMID 17270340.

At 6 months, breast events (gynecomastia, breast pain or both) occurred in 86.2%, 60.0%, 55.3%, 23.5% and 8.8% of men on tamoxifen 1, 2.5, 5, 10 and 20 mg, versus 96.7% on placebo. After tamoxifen stopped and bicalutamide continued for another 12 months, breast events were common in all groups at 24 months. Hot flushes rose at 5 mg or more.

Participants / model
282 men with prostate cancer on bicalutamide monotherapy
Treatment
Oral tamoxifen 1 to 20 mg daily or placebo, with bicalutamide 150 mg daily
Follow-up
12 months of tamoxifen, followed to 24 months
Study design
Randomized dose-response trial
Funding
not stated in the source

This is antiandrogen-induced gynecomastia, not gynecomastia from anabolic steroids. The protection did not last after tamoxifen stopped.

Read the original source
Meta-analysis of 9 randomized trials: tamoxifen RR 0.18 for gynecomastia

Systematic review and meta-analysis

Spagnolo L et al. J Endocrinol Invest. 2025;48(7):1659-1668. PMID 40244528.

Tamoxifen lowered the risk of gynecomastia (RR 0.18, 95% CI 0.08 to 0.38) and breast pain (RR 0.18, 95% CI 0.07 to 0.43), more than radiotherapy (gynecomastia RR 0.48, 95% CI 0.38 to 0.59), while anastrozole showed no significant benefit.

Participants / model
Men with prostate cancer on bicalutamide, 9 randomized trials
Treatment
Oral tamoxifen, oral anastrozole or breast radiotherapy versus bicalutamide alone or with placebo or sham
Follow-up
Pooled randomized trials
Study design
Systematic review and meta-analysis of 9 randomized trials
Funding
not stated in the source

Applies to men on bicalutamide.

Read the original source
Normal men and oligospermic men: LH, FSH, testosterone, estradiol up

Human study

Vermeulen A et al. Fertil Steril. 1978;29(3):320-7. PMID 640052.

In normal men, tamoxifen produced a moderate increase in LH, FSH, testosterone and estradiol, comparable to clomiphene 150 mg, and 6 weeks of tamoxifen increased the LH response to LHRH. In men with idiopathic oligospermia treated for 6 to 9 months, gonadotropins, testosterone and estradiol rose, but sperm density improved only in men below 20 million/mL with normal baseline FSH. Subject numbers are not given in the abstract.

Participants / model
Normal men; men with idiopathic oligospermia
Treatment
Oral tamoxifen 20 mg daily
Follow-up
10 days to 9 months
Study design
Clinical study
Funding
not stated in the source

Subject numbers are not given in the abstract.

Read the original source
PubMed search, 9 October 2026: 31 records, no controlled trial in steroid users

PubMed search record

PubMed search run on 9 October 2026: tamoxifen[tiab] AND (anabolic steroid*[tiab] OR anabolic-androgenic[tiab] OR anabolic androgenic[tiab] OR bodybuild*[tiab] OR post-cycle[tiab] OR "post cycle"[tiab]). 31 records returned.

The search returned 31 records: reviews (including the hypogonadism review on this page), case reports and case series (including an uncontrolled Spanish clinic series in which men whose sperm production had not recovered 6 months after stopping anabolic steroids were given tamoxifen 20 mg a day, with unpredictable response), surveys, drug-detection and seized-product analyses, a forum analysis, an internet search-interest analysis, a breast cancer treatment report in elderly patients, and animal or in-vitro studies. None was a controlled trial of tamoxifen for gynecomastia or hormonal recovery in anabolic steroid users.

Participants / model
Records returned, not a population
Treatment
Not applicable
Follow-up
Search run on 9 October 2026
Study design
Literature search
Funding
not stated in the source

A search result shows what PubMed returned on that date. It is not proof that no unindexed study exists.

Read the original source

Studies and sources

Tamoxifen tablet label, version effective 10 November 2025: male data, mechanism, PK

FDA prescribing information

DailyMed, U.S. National Library of Medicine. Tamoxifen citrate oral tablets, prescribing information, label version effective 10 November 2025. Set ID c82205a3-ae0c-4ce5-b04b-9581cd8c70d4.

The label says tamoxifen is effective for metastatic breast cancer in women and men; published results in 132 evaluable men with breast cancer showed a 50% objective response rate (66 responders). Its male safety text says literature and case reports suggest a safety profile in men similar to that in women, that loss of libido and impotence have led men to stop tamoxifen, and that in oligospermic men treated with tamoxifen, LH, FSH, testosterone and estrogen levels were elevated with no significant clinical changes reported. Tamoxifen is described as a nonsteroidal antiestrogen that competes with estradiol for estrogen receptor binding in tissues such as breast. After a single dose, plasma levels peaked at about 40 ng/mL about 5 hours later, and the terminal elimination half-life is about 5 to 7 days.

Participants / model
Women and men with breast cancer; oligospermic men (safety section); PK participants
Treatment
Tamoxifen citrate oral tablets
Follow-up
Label version effective 10 November 2025
Study design
FDA prescribing information
Funding
not stated in the source

The male statements come from literature and case reports summarized in the label, not from a labeled trial in men without cancer.

Read the original source
SOLTAMOX label, version effective 29 November 2021: 1977 approval, boxed warning, P-1

FDA prescribing information

DailyMed, U.S. National Library of Medicine. SOLTAMOX (tamoxifen citrate) oral solution, prescribing information, label version effective 29 November 2021. Set ID 1e6ff055-590c-41e6-9530-1fdf04cdbd02.

The label gives tamoxifen's initial US approval as 1977 and carries a boxed warning for uterine malignancies, stroke and pulmonary embolism, some fatal. Rates per 1,000 women-years in the NSABP P-1 prevention trial, tamoxifen versus placebo, were 2.20 versus 0.71 for endometrial adenocarcinoma, 0.17 versus 0.04 for uterine sarcoma, 1.43 versus 1.00 for stroke and 0.75 versus 0.25 for pulmonary embolism. In P-1, 13,388 women at high risk were randomized to tamoxifen or placebo for 5 years; after a median 4.2 years, invasive breast cancer fell 44% (86 versus 156 cases; RR 0.56, 95% CI 0.43 to 0.72), with no overall mortality difference.

Participants / model
Adults with breast cancer; women with ductal carcinoma in situ or at high risk (P-1)
Treatment
SOLTAMOX oral solution; P-1 used another tamoxifen formulation
Follow-up
Label version effective 29 November 2021; P-1 median follow-up 4.2 years
Study design
FDA prescribing information
Funding
not stated in the source

The boxed-warning rates are from women; no male thromboembolism or stroke rate was found. The uterine sarcoma placebo rate is taken as 0.04 per 1,000 women-years, the figure consistent with the boxed warning.

Read the original source
Drugs@FDA: SOLTAMOX approved 29 October 2005, generic tablets from 20 February 2003

Regulatory record

U.S. Food and Drug Administration. Drugs@FDA application record for NDA 021807 (SOLTAMOX), with generic tamoxifen citrate tablet applications such as ANDA 074732. Dates read from the openFDA Drugs@FDA records.

openFDA lists SOLTAMOX under NDA 021807, approved 29 October 2005, and generic tamoxifen citrate tablets under ANDAs approved from 20 February 2003 (for example ANDA 074732, Mylan). A query for the original NOLVADEX brand returned no openFDA record, so the 1977 year rests on the SOLTAMOX label.

Participants / model
Not a clinical population
Treatment
Drug applications
Follow-up
Approvals from 2003 to 2005
Study design
FDA application records
Funding
not stated in the source

These records give approval dates for the oral solution and generic tablets. The original 1977 approval is not in the openFDA record.

Read the original source
10 men, 1 month each: breast size down in 7 of 10

Randomized controlled trial

Parker LN et al. Metabolism. 1986;35(8):705-8. PMID 3526085.

Breast size decreased on tamoxifen in 7 of 10 men (P < 0.005), placebo had no effect, and all 4 men with painful gynecomastia had relief. The reduction was partial; at 9 to 12 months of follow-up in 8 men, one responder had tenderness return and one nonresponder grew.

Participants / model
10 men with benign gynecomastia
Treatment
Oral tamoxifen 10 mg twice daily or placebo, in random order
Follow-up
1 month per course
Study design
Double-blind randomized crossover trial
Funding
not stated in the source

Very small trial with a partial response.

Read the original source
81 men, uncontrolled cohort: 90.1% complete resolution

Human study

Mannu GS et al. Breast J. 2018;24(6):1043-1045. PMID 30079473.

90.1% (73 of 81) had complete resolution, and 2 of the 8 non-responders had surgery.

Participants / model
81 men (mean age 42.8) with primary (idiopathic) gynecomastia, 87.7% with breast pain
Treatment
Oral tamoxifen 10 mg daily
Follow-up
One UK breast clinic, 2004 to 2015
Study design
Prospective cohort study, uncontrolled
Funding
not stated in the source

There was no control group, so spontaneous regression cannot be separated from a drug effect.

Read the original source
282 men on bicalutamide: breast events 96.7% on placebo to 8.8% at the top dose

Randomized controlled trial

Fradet Y et al. Eur Urol. 2007;52(1):106-14. PMID 17270340.

At 6 months, breast events (gynecomastia, breast pain or both) occurred in 86.2%, 60.0%, 55.3%, 23.5% and 8.8% of men on tamoxifen 1, 2.5, 5, 10 and 20 mg, versus 96.7% on placebo. After tamoxifen stopped and bicalutamide continued for another 12 months, breast events were common in all groups at 24 months. Hot flushes rose at 5 mg or more.

Participants / model
282 men with prostate cancer on bicalutamide monotherapy
Treatment
Oral tamoxifen 1 to 20 mg daily or placebo, with bicalutamide 150 mg daily
Follow-up
12 months of tamoxifen, followed to 24 months
Study design
Randomized dose-response trial
Funding
not stated in the source

This is antiandrogen-induced gynecomastia, not gynecomastia from anabolic steroids. The protection did not last after tamoxifen stopped.

Read the original source
Meta-analysis of 9 randomized trials: tamoxifen RR 0.18 for gynecomastia

Systematic review and meta-analysis

Spagnolo L et al. J Endocrinol Invest. 2025;48(7):1659-1668. PMID 40244528.

Tamoxifen lowered the risk of gynecomastia (RR 0.18, 95% CI 0.08 to 0.38) and breast pain (RR 0.18, 95% CI 0.07 to 0.43), more than radiotherapy (gynecomastia RR 0.48, 95% CI 0.38 to 0.59), while anastrozole showed no significant benefit.

Participants / model
Men with prostate cancer on bicalutamide, 9 randomized trials
Treatment
Oral tamoxifen, oral anastrozole or breast radiotherapy versus bicalutamide alone or with placebo or sham
Follow-up
Pooled randomized trials
Study design
Systematic review and meta-analysis of 9 randomized trials
Funding
not stated in the source

Applies to men on bicalutamide.

Read the original source
European Academy of Andrology guideline: no SERMs or aromatase inhibitors for gynecomastia in general

Human study

Kanakis GA et al. Andrology. 2019;7(6):778-793. PMID 31099174.

The guideline recommends against using SERMs, aromatase inhibitors or non-aromatizable androgens to treat gynecomastia in general (strong recommendation, low-quality evidence), recommends watchful waiting after a causative substance is stopped, and reserves surgery for long-lasting gynecomastia.

Participants / model
Boys and men with gynecomastia (guideline scope)
Treatment
Not drug-specific
Follow-up
Not applicable
Study design
Clinical practice guideline (GRADE)
Funding
not stated in the source

It addresses treatment of gynecomastia, not prevention during antiandrogen therapy.

Read the original source
Normal men and oligospermic men: LH, FSH, testosterone, estradiol up

Human study

Vermeulen A et al. Fertil Steril. 1978;29(3):320-7. PMID 640052.

In normal men, tamoxifen produced a moderate increase in LH, FSH, testosterone and estradiol, comparable to clomiphene 150 mg, and 6 weeks of tamoxifen increased the LH response to LHRH. In men with idiopathic oligospermia treated for 6 to 9 months, gonadotropins, testosterone and estradiol rose, but sperm density improved only in men below 20 million/mL with normal baseline FSH. Subject numbers are not given in the abstract.

Participants / model
Normal men; men with idiopathic oligospermia
Treatment
Oral tamoxifen 20 mg daily
Follow-up
10 days to 9 months
Study design
Clinical study
Funding
not stated in the source

Subject numbers are not given in the abstract.

Read the original source
10 healthy men, 2 weeks each: tamoxifen raised LH 70% and testosterone 40%

Randomized controlled trial

Birzniece V et al. J Clin Endocrinol Metab. 2010;95(12):5443-8. PMID 20843951.

Tamoxifen and raloxifene both raised LH, FSH and testosterone, with larger mean rises on tamoxifen (testosterone 40% versus 25%; LH 70% versus 30%). At the higher dose tamoxifen also lowered IGF-I by 25% and raised SHBG by 20%.

Participants / model
10 healthy men
Treatment
Oral tamoxifen 10 and 20 mg daily and raloxifene 60 and 120 mg daily
Follow-up
2 weeks per drug
Study design
Randomized open-label crossover study
Funding
not stated in the source

Short hormone study in healthy men.

Read the original source
Review of AAS-induced hypogonadism: no quality studies met inclusion criteria

Human study

Rahnema CD et al. Fertil Steril. 2014;101(5):1271-9. PMID 24636400.

A review of anabolic steroid-induced hypogonadism was planned as a meta-analysis, but no quality studies met its inclusion criteria. Its management advice (judicious testosterone, hCG and SERMs) rests on published literature and expert opinion.

Participants / model
Men with symptomatic hypogonadism after nonprescribed anabolic steroid use
Treatment
Not drug-specific
Follow-up
Not applicable
Study design
Review; meta-analysis not possible
Funding
not stated in the source

The review shows how little controlled evidence existed for recovery treatment, not that a treatment works.

Read the original source
79 men after short steroid cycles: recovery with clomiphene, with or without hCG, versus none

Human study

İbis MA et al. BJU Int. 2026;137(1):154-165. PMID 41147237.

Both drug regimens sped hormonal recovery, but hormones normalized in all groups by month 6. Normozoospermia at 12 months was 87.5%, 69.2% and 58.6% with clomiphene plus hCG, clomiphene and no treatment.

Participants / model
79 recreational male anabolic steroid users who stopped after 6 months or less of use, with normal pre-cycle hormones and semen
Treatment
Expectant monitoring, clomiphene, or clomiphene plus hCG
Follow-up
Followed to 12 months
Study design
Retrospective two-center cohort study
Funding
not stated in the source

Tamoxifen was not studied. This is the most direct post-cycle comparison found, and it was not randomized.

Read the original source
Review of tamoxifen adverse events in men: varied by population, fewer than 5% withdrew

Human study

Wibowo E et al. Andrology. 2016;4(5):776-88. PMID 27152880.

The adverse-event profile varied by population: few adverse events in men treated for infertility or idiopathic gynecomastia, more in men with prostate or breast cancer, and fewer than 5% withdrawing for toxicity, most of them male breast cancer patients stopping for cardiovascular events. The authors note that long-term studies documenting side effects in men are lacking.

Participants / model
Men in published randomized and non-randomized tamoxifen studies (prostate cancer, breast cancer, infertility, idiopathic gynecomastia)
Treatment
Oral tamoxifen, various doses
Follow-up
Not applicable
Study design
Review of adverse events
Funding
not stated in the source

Long-term studies documenting side effects in men are lacking.

Read the original source
PubChem: tamoxifen and tamoxifen citrate identity

Chemical identity record

National Library of Medicine. PubChem compound records CID 2733526 (tamoxifen) and CID 2733525 (tamoxifen citrate).

Tamoxifen base: PubChem CID 2733526, C26H29NO, 371.5 g/mol, CAS 10540-29-1; the label describes it as the trans isomer of a triphenylethylene derivative. Tamoxifen citrate, the salt in US tablets: CID 2733525, C32H37NO8, 563.6 g/mol, CAS 54965-24-1. Label doses are expressed as tamoxifen, not the citrate salt.

Participants / model
Chemical identity, not a clinical population
Treatment
Defined molecule and salt
Follow-up
Not applicable
Study design
NLM chemical record
Funding
not stated in the source

Identity record only; it says nothing about efficacy or safety. Salt and base masses differ, so they are not interchangeable.

Read the original source

Why is Tamoxifen in A tier?

A fits an approved drug promoted for an off-label use. Tamoxifen has been FDA-approved since 1977 and has very large randomized trials in women. In men it has randomized support for preventing gynecomastia in men starting bicalutamide, but gynecomastia from steroids and post-cycle recovery had no controlled trial in the PubMed search run on 9 October 2026.