Enclomiphene and Clomid: one molecule, two halves

How both work

Your brain watches estrogen levels as a signal of how much testosterone is circulating, since some testosterone is converted to estrogen. Selective estrogen receptor modulators (SERMs) like clomiphene and enclomiphene block estrogen's feedback at the hypothalamus and pituitary. The brain responds by releasing more luteinizing hormone (LH) and follicle-stimulating hormone (FSH), which tell the testes to make more testosterone and support sperm production.

This approach only works if the brain's signaling and the testes are both capable of responding, which is why it is used for secondary hypogonadism rather than testicular failure.

Two isomers with different personalities

Clomiphene citrate is a roughly 60:40 mixture of two isomers. Enclomiphene (the trans form) is the more potent anti-estrogen at the brain and drives most of the rise in LH and testosterone. Zuclomiphene (the cis form) has a much longer half-life, can build up over weeks of daily dosing, and has some estrogen-like activity.

The theory behind enclomiphene is that removing zuclomiphene could give the same testosterone benefit with fewer estrogen-related side effects such as mood changes or breast tenderness. That theory is plausible, but head-to-head trials in men comparing the two directly are limited.

What the trials show for enclomiphene

Phase III trials published in BJU International studied overweight men aged 18 to 60 with secondary hypogonadism. Over 16 weeks, oral enclomiphene raised total testosterone, LH and FSH and kept sperm concentration in the normal range. In the comparison group, testosterone gel also raised testosterone but lowered LH and FSH and markedly reduced sperm production.

Despite those results, enclomiphene was never approved by the FDA. In 2022 the FDA's Pharmacy Compounding Advisory Committee voted against adding it to the 503A bulks list. It remains available through compounding pharmacies, and its long-term safety data are limited.

Clomiphene's track record

Clomiphene has been used for decades. MedlinePlus describes its approved use as inducing ovulation in women and notes it is sometimes used to treat male infertility. Urology guidelines list SERMs among options for men with low testosterone who want to preserve fertility.

Because it is FDA-approved, clomiphene is made to FDA manufacturing standards, which some men and clinicians value. Its downside in men is the zuclomiphene component and the off-label status.

Side effects both can cause

• Visual symptoms such as blurring, spots or flashes, which need prompt medical attention
• Headache, flushing and mood changes
• Breast tenderness, especially if estradiol rises
• A small risk of blood clots, as with other SERMs
• Higher hematocrit in some men as testosterone rises

Practical differences day to day

Clomiphene for men is usually taken as a swallowed tablet on a schedule set by the prescriber, often not every day, because zuclomiphene's long half-life lets it accumulate. Enclomiphene has a shorter half-life, so it is generally taken daily. The HealifyMD product is an orally dissolving tablet that melts on or under the tongue.

Both require the same monitoring. Expect labs a few weeks after starting to check testosterone, LH, FSH, estradiol and hematocrit, and a symptom check-in to see whether energy, libido, mood and sleep have changed. If levels rise but you feel no different after a few months, the plan should be revisited rather than continued by default.

Neither medicine is right for men with a history of blood clots, active liver disease or unexplained vision problems. Tell your clinician about every medicine and supplement you take, including anything bought for bodybuilding or 'testosterone support.'

Choosing between them

For most men the choice comes down to preferences about regulatory status, side effects and cost, discussed with a clinician. Some prefer an FDA-approved drug used off-label; others prefer the single-isomer approach. Either way, the diagnosis comes first: the AUA recommends confirming low testosterone with two early-morning measurements and checking LH, and both drugs require follow-up labs.

The HealifyMD Enclomiphene / DHEA / Boron / Pregnenolone ODT is compounded by a licensed U.S. pharmacy. Compounded medications are not FDA-approved, are not reviewed by the FDA for safety, effectiveness or quality, and are not interchangeable with any branded product. It costs from $129/month, or $349 for three months ($116/month), with no membership fee, confirmed at the eligibility review; labs are priced separately.