Enclomiphene, Low Testosterone, and the Men Who Still Want Children

A common visit goes like this, a man in his late thirties comes in tired, thick around the middle, and sleeping badly, and his morning total testosterone comes back at 240 ng/dL. He's read enough to know what usually happens next, a weekly injection or a daily gel, and he asks the question that should stop the conversation cold. He and his wife want another child in a year or two, so is testosterone a problem? It is, and the reason matters before anyone writes a prescription.

Replacing testosterone shuts down the factory

Your testes don't make testosterone on their own initiative. The hypothalamus and pituitary, two small structures at the base of the brain, release luteinizing hormone (LH) and follicle-stimulating hormone (FSH), and those two signals tell the testes to produce testosterone and to make sperm. When you inject or rub on testosterone from outside, the brain reads the high blood level, concludes that nothing more is needed, and cuts LH and FSH, so the testes go quiet. Intratesticular testosterone, the concentrated pool inside the testis that sperm production depends on, collapses even while the blood level looks excellent on paper.

Crosnoe and colleagues laid this out in a 2013 review in Translational Andrology and Urology, describing exogenous testosterone as a preventable cause of male infertility and reporting that most men recover sperm production within a year of stopping [1]. The alternatives that protect the testis are human chorionic gonadotropin and selective estrogen receptor modulators, which is where enclomiphene enters.

What enclomiphene is

Enclomiphene is the trans-isomer of clomiphene citrate, a selective estrogen receptor modulator (SERM), which means it occupies estrogen receptors and blocks estrogen's signal in some tissues while mimicking it in others. Estrogen is what tells the hypothalamus and pituitary to stop pushing, so blocking that message raises LH and FSH, the testes make more of their own testosterone, and because FSH keeps arriving, sperm production continues.

Clomiphene, the drug sold for decades as Clomid and FDA-approved for ovulation induction in women, isn't one molecule but a mixture of two mirror-image forms that behave differently. Rodriguez and colleagues, reviewing the compound in Expert Opinion on Pharmacotherapy in 2016, described enclomiphene as the isomer that raises LH and FSH, with a half-life around 10 hours, while zuclomiphene acts as an estrogen receptor agonist with a half-life of roughly 30 days, so it accumulates and carries the estrogen-like side effects [2]. Helo and colleagues confirmed that accumulation in 15 hypogonadal men taking clomiphene 25 mg daily for at least six weeks, finding a median zuclomiphene to enclomiphene ratio of 20 to 1 [3]. A man on Clomid is, after a month or two, mostly carrying the isomer nobody wanted, which is the rationale for purifying out the trans-isomer.

What the randomized trials found

Three trials compared enclomiphene directly against topical testosterone, and they agree. Kaminetsky and colleagues, in a 2013 randomized study in the Journal of Sexual Medicine, treated 12 men with secondary hypogonadism and found that both drugs raised total testosterone and held it for six months, while only the enclomiphene group showed rising LH and FSH. Sperm concentrations on enclomiphene ran from 75 to 334 million per mL, and the gel failed to lift counts above 20 million per mL in any of the five men at three months [4]. A larger randomized phase II trial in Fertility and Sterility in 2014 reported the same result [5].

The phase III program tested it in exactly the men we see. Kim and colleagues ran two parallel randomized, double-blind, placebo-controlled trials in overweight men aged 18 to 60 with morning testosterone at or below 300 ng/dL. Over 16 weeks testosterone rose in every treatment group, while LH and FSH rose on enclomiphene and fell on testosterone gel. Enclomiphene held sperm concentration in the normal range, and the gel produced a marked reduction in sperm production [6]. The dose data come from a pharmacodynamic study comparing 6.25, 12.5 and 25 mg daily against transdermal testosterone in 48 men, where after six weeks the 25 mg dose produced a mean total testosterone of 604 ng/dL against 500 ng/dL on the gel, a difference that wasn't statistically significant [7].

A 2025 meta-analysis of the randomized trials of both SERMs reached the same answer, with clomiphene or enclomiphene raising total testosterone by about 274 ng/dL versus placebo, raising LH and FSH, and performing no differently from testosterone gel [8].

Why the FDA said no anyway

The trials above convinced almost everyone except the regulator. Enclomiphene has been in front of the FDA since 2007, and the agency declined to approve it on the grounds that raising the testosterone number alone wasn't sufficient evidence of benefit, rejecting normalized LH and quality-of-life scores as indications as well [2]. The manufacturer discontinued development in 2021 and the European Medicines Agency never approved it either, as the British Society for Sexual Medicine documented in its 2026 position statement, which notes that enclomiphene remains available through compounding pharmacies and advises clinicians to counsel patients about the missing long-term data [9]. The compounded capsules we prescribe are therefore not an FDA-approved product, while clomiphene, its impure parent, is FDA-approved only for women.

I think that objection was narrow rather than a verdict that the drug fails, though it points at a real gap. Almost every enclomiphene study measured hormones and semen, not how men felt, and none evaluated symptoms or quality of life with validated instruments [2]. The evidence that this drug moves your lab value is strong, and the evidence that it fixes your energy, libido, or body composition is thin. I'd rather tell you that than sell you the number.

Safety, and who should stay away

Long-term data come mostly from clomiphene rather than the purified isomer. Krzastek and colleagues reviewed 400 men treated with clomiphene for hypogonadism and found that among the 120 treated beyond three years, 88 percent reached normal testosterone, 77 percent reported improved symptoms, and 8 percent reported side effects, most often mood changes, blurred vision and breast tenderness, with no serious adverse events [10]. Blurred vision warrants stopping the drug and calling your physician.

SERMs as a class carry a venous thromboembolism signal, and clomiphene has produced case reports of it in men, including a large-volume pulmonary embolism in a 56-year-old man two years into treatment [11]. Case reports can't establish how often this happens, though a personal or family history of clotting belongs in the conversation before you start. Men with primary hypogonadism, where the testes themselves have failed, won't respond, because there's no factory to restart. Competitive athletes should stay away entirely, since clomiphene sits in section 4.2 of the World Anti-Doping Agency prohibited list and is banned both in and out of competition [12].

The unglamorous part that works

Secondary hypogonadism in a middle-aged man is usually not a pituitary disease. It's the metabolic consequence of visceral fat, insulin resistance, and fractured sleep, and reversing those raises testosterone without a prescription. Corona and colleagues, in a 2013 meta-analysis in the European Journal of Endocrinology, pooled 24 studies and found that a low-calorie diet raised total testosterone and bariatric surgery raised it roughly three times as much, with the degree of weight loss the single best predictor of how much testosterone came back [13]. Sleep-disordered breathing pulls the same way, and a meta-analysis of 18 studies covering 1,823 men found testosterone inversely associated with obstructive sleep apnea independent of age and body mass index [14].

This means the order of operations matters more than the molecule. Before we prescribe anything, we check a morning total and free testosterone on two separate days, LH, FSH, estradiol, prolactin, a hematocrit, and the panel that shows what's driving the number, including fasting insulin and the rest of the core metabolic labs. We screen for sleep apnea in anyone who snores or wakes unrefreshed, since sleep is where mitochondria and hormones both get repaired, and we push on body composition first, because losing visceral fat treats the cause.

When a man has confirmed secondary hypogonadism, wants to preserve fertility, and has done that work, enclomiphene is a defensible choice, and we recheck testosterone, LH, FSH, estradiol and a semen analysis rather than assuming it worked. If you're on testosterone now and want children, don't stop on your own, since there are established ways to restart the axis.

Ask a provider about enclomiphene

References

1. Crosnoe LE, Grober E, Ohl D, et al. Exogenous testosterone: a preventable cause of male infertility. Transl Androl Urol. 2013. PMID: 26813847
2. Rodriguez KM, Pastuszak AW, Lipshultz LI. Enclomiphene citrate for the treatment of secondary male hypogonadism. Expert Opin Pharmacother. 2016. PMID: 27337642
3. Helo S, Mahon J, Ellen J, et al. Serum levels of enclomiphene and zuclomiphene in men with hypogonadism on long-term clomiphene citrate treatment. BJU Int. 2017. PMID: 27511863
4. Kaminetsky J, Werner M, Fontenot G, et al. 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. PMID: 23530575
5. Wiehle RD, Fontenot GK, Wike J, et al. Enclomiphene citrate stimulates testosterone production while preventing oligospermia: a randomized phase II clinical trial comparing topical testosterone. Fertil Steril. 2014. PMID: 25044085
6. 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. PMID: 26496621
7. Wiehle R, Cunningham GR, Pitteloud N, et al. Testosterone restoration by enclomiphene citrate in men with secondary hypogonadism: pharmacodynamics and pharmacokinetics. BJU Int. 2013. PMID: 23875626
8. Hohl A, Chavez MP, Pasqualotto E, et al. Clomiphene or enclomiphene citrate for the treatment of male hypogonadism: a systematic review and meta-analysis of randomized controlled trials. Arch Endocrinol Metab. 2025. PMID: 41066380
9. Foster J, Choo L, Patel A, et al. British Society of Sexual Medicine: position statement for the potential use of enclomiphene in the treatment of male hypogonadism. World J Mens Health. 2026. PMID: 41714894
10. Krzastek SC, Sharma D, Abdullah N, et al. Long-term safety and efficacy of clomiphene citrate for the treatment of hypogonadism. J Urol. 2019. PMID: 31216250
11. Solipuram V, Pokharel K, Ihedinmah T. Pulmonary embolism as a rare complication of clomiphene therapy: a case report and literature review. Case Rep Endocrinol. 2021. PMID: 34540296
12. Nair VS, Heybroek M, Miller GD, et al. Distribution of clomiphene and its metabolites in antidoping samples, a 3-year perspective. Drug Test Anal. 2026. PMID: 41672565
13. Corona G, Rastrelli G, Monami M, et al. Body weight loss reverts obesity-associated hypogonadotropic hypogonadism: a systematic review and meta-analysis. Eur J Endocrinol. 2013. PMID: 23482592
14. Su L, Meng YH, Zhang SZ, et al. Association between obstructive sleep apnea and male serum testosterone: a systematic review and meta-analysis. Andrology. 2022. PMID: 34536053