TRT vs Enclomiphene: How They Differ for Low Testosterone

Both raise testosterone, but in opposite ways. One supplies the hormone from outside, the other pushes the body to make more of its own. That difference drives everything else: fertility, who each works for, and why one is an approved drug while the other isn't.

TRT and enclomiphene both raise testosterone, but in opposite ways. TRT delivers testosterone from outside. The brain reads the higher level and turns down luteinizing hormone (LH) and follicle-stimulating hormone (FSH), which suppresses sperm production. That is why the AUA guideline says exogenous testosterone should not be prescribed to men who are trying to conceive². Enclomiphene is an oral selective estrogen receptor modulator (SERM). It blocks estrogen feedback at the hypothalamus and pituitary, LH and FSH rise, and the testes produce more testosterone of their own³. It needs a working pituitary and working testes, so it applies only to secondary hypogonadism³. The other major difference is status. TRT products are FDA-approved. Enclomiphene is not: the FDA declined to approve it in 2015¹⁰, the EMA refused it in 2018¹¹, and its trials measured hormone levels and sperm rather than symptoms¹¹. For TRT itself, see the TRT hub.

TRT vs enclomiphene at a glance

What enclomiphene is

Enclomiphene is one of the two isomers that make up clomiphene citrate (Clomid). The FDA label describes clomiphene as a mixture of the cis isomer, zuclomiphene, and the trans isomer, enclomiphene, with 30–50% cis⁴. The two behave differently. A 2016 review gives enclomiphene a half-life of about 10 hours, while zuclomiphene's is on the order of 30 days. The review argues that the long-lived zuclomiphene accounts for side effects that outlast clomiphene's therapeutic effect³. Leaving that isomer out is the rationale for developing enclomiphene as a drug on its own³.

Clomiphene itself is FDA-approved, but only for ovulatory dysfunction in women who want to become pregnant. Its label says there are no adequate or well-controlled studies showing it works for male infertility, and that testicular tumors and gynecomastia have been reported in men who used it. The label also warns about visual symptoms, which can be irreversible, especially at higher doses or with longer use⁴. The Endocrine Society guideline notes that clomiphene has been used empirically in men with hypogonadotropic hypogonadism, "however, neither its efficacy nor its safety has been demonstrated in randomized trials"¹.

Fertility: the reason this comparison exists

Both major guidelines treat sperm suppression as the key limitation of TRT for men who want children. The Endocrine Society recommends against testosterone therapy in men planning fertility in the near term, and says it is not appropriate for men with hypogonadotropic hypogonadism who want children within 6 to 12 months. Men who aren't sure may want to bank sperm if they are not azoospermic¹. The AUA guideline says testosterone should be stopped before trying to conceive and that recovery is unpredictable: in contraceptive studies, two-thirds of men had sperm back in the ejaculate within six months of stopping, but 10% took until the second year². The FDA label for testosterone cypionate notes that oligospermia can occur after prolonged use or excessive dosage¹⁵.

The enclomiphene trials were designed around exactly that problem:

1. In a small randomized phase IIB study of 12 men with secondary hypogonadism, enclomiphene raised testosterone to levels comparable to testosterone gel after six months, and raised sperm counts in every man who completed the three- and six-month assessments. Gel raised counts above 20 million/mL in only two of five men.
2. A randomized phase II trial comparing enclomiphene with topical testosterone found similar morning testosterone levels. LH and FSH rose on enclomiphene, sperm counts were preserved, and estradiol also rose.
3. Two parallel phase III trials in overweight men aged 18–60 with secondary hypogonadism ran for 16 weeks. Testosterone rose in all treatment groups. LH and FSH went up on enclomiphene and down on testosterone gel, and sperm concentration stayed in the normal range on enclomiphene but dropped markedly on gel.
4. A 2025 meta-analysis of 10 randomized trials (819 men), which pooled clomiphene and enclomiphene, found no difference in total testosterone between SERMs and testosterone gel. LH and FSH were higher with SERMs, sperm concentration was about 70 million/mL higher, and the risk of falling below 15 million/mL was about 90% lower (relative risk 0.10).

Sources for the list above, in order: Kaminetsky 2013⁵, Wiehle 2014⁶, Kim 2016⁷ and Hohl 2025⁸. The AUA guideline allows clinicians to use SERMs, aromatase inhibitors, hCG or a combination in men with testosterone deficiency who want to maintain fertility. That is a conditional recommendation based on grade C evidence, and the guideline adds that of these agents only hCG is FDA-approved for men². It also names men with low or low-normal LH as candidates for SERM therapy, particularly those who want to preserve fertility².

What the evidence does not show

Regulators and reviewers keep pointing to the same gap. When the EMA's committee refused authorization for enclomiphene (as EnCyzix) in January 2018, it noted that the four main studies, with 588 patients, showed higher testosterone but did not examine whether symptoms such as bone strength, weight gain, impotence and libido improved. It also cited a risk of venous thromboembolism and concluded that the benefits did not outweigh the risks¹¹. The FDA's 2015 complete response letter, as disclosed by the sponsor, said the phase 3 design was "no longer adequate to demonstrate clinical benefit" and recommended further phase 3 studies¹⁰.

Newer reviews haven't closed that gap. The 2025 meta-analysis rated the hormone results moderate certainty but said the analysis "remains underpowered with regard to safety endpoints", with follow-up of 2 to 30 weeks⁸. A 2024 retrospective study of 66 men compared enclomiphene with clomiphene. Enclomiphene had lower odds of adverse events and a smaller effect on estradiol, but the study was observational and short⁹. A 2026 British Society for Sexual Medicine position statement cites the absence of long-term efficacy and safety data and advises that enclomiphene use be limited to experienced clinicians in specialist or research settings, with patients counselled about its unlicensed status¹⁴.

Regulatory status and the compounding caveat

The 503A list matters because it defines which bulk substances a pharmacy may use to compound drugs that have no FDA-approved version. Anyone considering a compounded product should also know the FDA's general position: "Compounded drugs are not FDA-approved. This means that FDA does not verify the safety, effectiveness or quality of compounded drugs before they are marketed"¹³. The AUA takes the same view of testosterone itself, preferring commercially manufactured products over compounded ones because pharmacy preparations vary in potency and quality². For enclomiphene there is no approved version to fall back on, so every product in circulation carries that caveat.

Who each fits, according to the literature

The guidelines don't pit the two against each other directly. Taken together, though, they describe a clear split:

1. TRT is the guideline-backed treatment for men with symptoms and consistently low testosterone who are not planning to conceive in the near term. It works whether the cause is testicular (primary) or pituitary/hypothalamic (secondary).
2. A SERM such as enclomiphene is discussed for secondary hypogonadism, meaning low testosterone with low or low-normal LH, mainly when preserving fertility is the priority.
3. The BSSM statement adds needle aversion and intolerance of injectable or topical testosterone as situations where enclomiphene might be considered, always within secondary hypogonadism and a specialist setting.
4. Enclomiphene has no role in primary hypogonadism. If the testes cannot respond to LH, raising LH does not help.

Sources for the list: the Endocrine Society guideline¹, the AUA guideline², the BSSM position statement¹⁴ and the 2016 enclomiphene review³. Telling primary from secondary hypogonadism is why baseline LH and FSH are part of the workup. The TRT bloodwork guide explains that panel.

Monitoring on either path

Either route calls for scheduled labs. On TRT, the Endocrine Society schedule checks testosterone and hematocrit at 3–6 months and then annually¹. Hematocrit is the value most likely to force a change, which the high hematocrit on TRT guide covers in detail. For men on clomiphene, anastrozole or hCG, the AUA recommends testing testosterone no earlier than four weeks after starting². Estradiol also needs attention on a SERM: it rose in the enclomiphene trials⁶, and in the 2025 meta-analysis it was about 18 pg/mL higher on SERMs than on testosterone gel⁸. The estradiol on TRT guide explains how to read that number and why the assay matters. For how symptoms tend to change on TRT over the first year, see the TRT results timeline. For protocols built around steadier levels, see TRT microdosing and SubQ vs IM testosterone.

Whichever route your prescriber chooses, keep medication, dose and lab results on one timeline so you can compare the two honestly if you ever switch. Peptide Me lets you log any prescribed medication next to your bloodwork, chart testosterone, LH, estradiol and hematocrit over time, and export a summary for your appointment.

Disclaimer: this article summarizes guidelines, regulatory decisions and published studies comparing testosterone therapy and enclomiphene. It is not medical advice and does not recommend either treatment. Testosterone is a prescription, controlled medication, and enclomiphene is not an FDA-approved drug. Which option, if any, suits you depends on the cause of your low testosterone, your fertility plans and your health history, and that decision should be made with a qualified clinician.

FAQ

References

Primary sources — PubMed / NEJM / The Lancet.

1. Bhasin S, Brito JP, Cunningham GR, et al. Testosterone Therapy in Men With Hypogonadism: An Endocrine Society Clinical Practice Guideline. J Clin Endocrinol Metab. 2018;103(5):1715-1744. https://academic.oup.com/jcem/article/103/5/1715/4939465
2. Mulhall JP, Trost LW, Brannigan RE, et al. Evaluation and Management of Testosterone Deficiency: AUA Guideline. J Urol. 2018;200(2):423-432. https://www.auanet.org/documents/Guidelines/PDF/Testosterone-Deficiency-JU.pdf
3. Rodriguez KM, Pastuszak AW, Lipshultz LI. Enclomiphene citrate for the treatment of secondary male hypogonadism. Expert Opin Pharmacother. 2016;17(11):1561-1567. https://pmc.ncbi.nlm.nih.gov/articles/PMC5009465/
4. DailyMed. CLOMID (clomiphene citrate) tablet — Prescribing Information. U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed/lookup.cfm?setid=f15e9918-6001-4150-bd54-1364a6febcb8
5. Kaminetsky J, Werner M, Fontenot G, Wiehle RD. Oral enclomiphene citrate stimulates the endogenous production of testosterone and sperm counts in men with low testosterone: comparison with testosterone gel. J Sex Med. 2013;10(6):1628-1635. https://pubmed.ncbi.nlm.nih.gov/23530575/
6. Wiehle RD, Fontenot GK, Wike J, Hsu K, Nydell J, Lipshultz L; ZA-203 Clinical Study Group. Enclomiphene citrate stimulates testosterone production while preventing oligospermia: a randomized phase II clinical trial comparing topical testosterone. Fertil Steril. 2014;102(3):720-727. https://pubmed.ncbi.nlm.nih.gov/25044085/
7. Kim ED, McCullough A, Kaminetsky J. Oral enclomiphene citrate raises testosterone and preserves sperm counts in obese hypogonadal men, unlike topical testosterone: restoration instead of replacement. BJU Int. 2016;117(4):677-685. https://pubmed.ncbi.nlm.nih.gov/26496621/
8. Hohl A, Chavez MP, Pasqualotto E, Ferreira ROM, Sande-Lee SV, Ronsoni MF. Clomiphene or enclomiphene citrate for the treatment of male hypogonadism: a systematic review and meta-analysis of randomized controlled trials. Arch Endocrinol Metab. 2025;69(5):e250093. https://pmc.ncbi.nlm.nih.gov/articles/PMC12510335/
9. Saffati G, Kassab J, Orozco Rendon D, et al. Safety and efficacy of enclomiphene and clomiphene for hypogonadal men. Transl Androl Urol. 2024;13(9):1984-1990. https://pmc.ncbi.nlm.nih.gov/articles/PMC11491226/
10. Repros Therapeutics Inc. Repros Therapeutics Receives Complete Response Letter From FDA for Enclomiphene (press release filed with the U.S. SEC). December 1, 2015. https://www.sec.gov/Archives/edgar/data/897075/000117184315006596/newsrelease.htm
11. European Medicines Agency. Refusal of the marketing authorisation for EnCyzix (enclomifene). EMA/CHMP/54473/2018. 26 January 2018. https://www.ema.europa.eu/en/documents/smop-initial/questions-and-answers-refusal-marketing-authorisation-encyzix-enclomifene_en.pdf
12. U.S. Food and Drug Administration. Final Summary Minutes of the Pharmacy Compounding Advisory Committee Meeting, June 8, 2022. https://www.fda.gov/media/161293/download
13. U.S. Food and Drug Administration. Compounding and the FDA: Questions and Answers. https://www.fda.gov/drugs/human-drug-compounding/compounding-and-fda-questions-and-answers
14. Foster J, Choo L, Patel A, Kirby M, Hackett G. British Society of Sexual Medicine: Position Statement for the Potential Use of Enclomiphene in the Treatment of Male Hypogonadism. World J Mens Health. 2026;44(3):480-483. https://pmc.ncbi.nlm.nih.gov/articles/PMC13302965/
15. DailyMed. DEPO-TESTOSTERONE (testosterone cypionate) injection, solution — Prescribing Information. U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=cfbb53d4-b868-4a28-8436-f9112eb01c39