Selective estrogen receptor modulator (SERM) · Investigational (compounded only)
An estrogen-blocking molecule that prompts the body to make more of its own testosterone, studied for men with secondary low testosterone who want to preserve fertility.
✦ 2 min read · 2 sourcesWhat it is
Enclomiphene is the trans-isomer of clomiphene, a selective estrogen receptor modulator (SERM). It is not FDA-approved for any indication; developer Repros Therapeutics submitted a New Drug Application for secondary hypogonadism that the FDA did not approve, partly because regulators did not accept a testosterone increase alone as sufficient evidence. Today it is available in the U.S. only through compounding pharmacies with a prescription.
How it works
By blocking estrogen receptors in the hypothalamus and pituitary, enclomiphene reduces estrogen's negative feedback on the brain. The pituitary responds by releasing more luteinizing hormone (LH) and follicle-stimulating hormone (FSH), which signal the testes to produce more testosterone and support sperm production.
What the evidence shows
Phase 3 trials (including studies ZA-304 and ZA-305) in overweight and obese men with secondary hypogonadism showed enclomiphene consistently restored serum total testosterone into the normal range while raising LH and FSH, confirming it works through the body's own hormonal axis. Earlier pharmacokinetic and pharmacodynamic studies corroborated these effects. The honest gap is that no formulation ever cleared FDA review, and long-term outcome data (versus surrogate hormone levels) remain limited.
Quick check
Four questions, ~60 seconds, with a sourced result.
The honest take
Multiple Phase 3 trials show it reliably raises testosterone, but it has never gained FDA approval, so it remains investigational and compounded.
Status & safety
Enclomiphene is investigational and not FDA-approved; legitimate access is via a prescription filled at a compounding pharmacy after medical evaluation and hormone testing. As a SERM (a clomiphene isomer), it is prohibited at all times in sport under WADA category S4 (hormone and metabolic modulators), and a Therapeutic Use Exemption would be required for any athlete. Potential effects and risks should be discussed with a clinician.
Summaries of published, third-party research for educational purposes. Not medical advice; not a claim of efficacy or safety for any use.
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