Enclomiphene for Testosterone Support — Testosterone & Androgens
Pure trans-isomer of clomiphene that raises testosterone without the estrogenic accumulation of zuclomiphene.
Overview
Enclomiphene is the isolated trans-isomer of clomiphene citrate, possessing purely anti-estrogenic activity at the hypothalamic-pituitary level without the complicating estrogenic effects of its cis-isomer (zuclomiphene). By selectively blocking estrogen receptors in the hypothalamus, enclomiphene stimulates the HPG axis, increasing LH, FSH, and endogenous testosterone production while preserving fertility. Phase 2 and 3 clinical trials (ZA-203, ZA-204, ZA-301, ZA-302) demonstrated that enclomiphene 12.5-25 mg daily significantly increased testosterone levels (mean increase to 450-600 ng/dL from baseline ~230 ng/dL) while maintaining or improving sperm parameters. Unlike clomiphene citrate, enclomiphene has a short half-life (~10 hours) and does not accumulate, potentially reducing the visual and mood side effects associated with chronic zuclomiphene exposure. Despite completing Phase 3 trials, enclomiphene has not received FDA approval — Repros Therapeutics received a Complete Response Letter from the FDA in 2015 citing manufacturing concerns, and the product remains unapproved. It is currently available through compounding pharmacies and is one of the most rapidly growing compounds in the TRT-adjacent market.
Indications
- Investigational: Secondary hypogonadism with fertility preservation
- Off-label (compounded): Testosterone support as alternative to TRT
- Off-label (compounded): Post-cycle therapy
- Off-label (compounded): HPG axis restart after steroid use
Mechanism of Action
Blocks estrogen receptor alpha exclusively in the hypothalamus and pituitary without estrogenic agonist activity
Dosing
| Compound | Dose | Frequency | Notes |
|---|---|---|---|
| Enclomiphene | 12.5 mg | Once daily | Standard starting dose from clinical trials |
| Enclomiphene | 25 mg | Once daily | Higher dose for insufficient response |
| Enclomiphene | 6.25 mg | Once daily | Low dose for sensitive individuals or maintenance |
Evidence Grade
GRADE B
Safety & Contraindications
- Not FDA-approved — available only through compounding pharmacies
- Long-term safety data limited compared to clomiphene
- Headache, hot flashes, and nausea reported in clinical trials
- Quality control varies between compounding pharmacies
- Potential for elevated estradiol as testosterone rises (may need AI)
- Monitor for visual disturbances though risk lower than clomiphene