Enclomiphene: A Selective Estrogen Receptor Modulator for Testosterone Support

This article is for informational purposes only and does not constitute medical advice. Superpower Health facilitates access to enclomiphene through licensed providers and compounding pharmacy partners. Always consult a qualified healthcare provider before starting any prescription compound.

Standard testosterone replacement works. It also shuts down the signaling loop that tells your body to produce testosterone on its own. For men who want higher levels without sacrificing endogenous production or fertility, that tradeoff has been the central problem. Enclomiphene was designed around it.

Here is how enclomiphene works as a selective estrogen receptor modulator (SERM), what the clinical data shows compared to exogenous testosterone, and how providers evaluate candidacy.

Key Takeaways

• Regulatory Status: Not FDA-approved. The Androxal NDA received a Complete Response Letter in 2015. Available only through compounding by prescription from a licensed provider.
• Research Stage: Phase II and III RCT data available; available through compounding
• Availability: Prescription only; available through Superpower's licensed provider network and compounding pharmacy partners. Enclomiphene is not available in all states. It is currently not available in New York or New Jersey.
• Prescribing information: View compound reference data (PubChem CID 1548953)
• How it works: Blocks estrogen receptors in the hypothalamus and pituitary, stimulating LH and FSH release and endogenous testosterone production.
• What the research shows: In two Phase III RCTs of 256 overweight men aged 18–60 with secondary hypogonadism (baseline total testosterone ≤300 ng/dL), enclomiphene raised mean testosterone from ~205 ng/dL to 413–446 ng/dL at 16 weeks (p = 0.0007 and p = 0.0368 vs. placebo) while maintaining sperm concentration. Comparative data with topical testosterone (AndroGel 1.62%) from the same trials showed different fertility preservation profiles; this comparison is for scientific context only, as enclomiphene and FDA-approved TRT have fundamentally different regulatory statuses.

What Is Enclomiphene?

Enclomiphene (brand name Androxal; received a Complete Response Letter in 2015) is the trans-isomer of clomiphene, a drug used in fertility medicine for decades. Clomiphene is a racemic mixture of two isomers: enclomiphene (the trans-isomer) and zuclomiphene (the cis-isomer). These isomers have distinct pharmacological profiles. Enclomiphene acts primarily as an estrogen receptor antagonist. Zuclomiphene acts as a partial agonist and accumulates in tissue with chronic use. The NDA for Androxal received a Complete Response Letter in 2015; the FDA cited concerns about study design adequacy and clinical benefit demonstration, and recommended additional Phase 3 studies that were never completed. As a result, enclomiphene is not FDA-approved and is available only through licensed compounding pharmacies by prescription.

How Enclomiphene Works in the Body

Estrogen Receptor Blockade at the Hypothalamus and Pituitary

Enclomiphene binds to estrogen receptors in the hypothalamus and anterior pituitary without activating them. This competitive blockade prevents circulating estrogen from signaling "enough testosterone is present." In the normal HPG axis (hypothalamic-pituitary-gonadal axis), estrogen exerts negative feedback that suppresses GnRH, LH, and FSH release. By blocking this feedback, enclomiphene removes the brake on the system. The pituitary responds by releasing more luteinizing hormone (LH) and follicle-stimulating hormone (FSH). LH then signals the Leydig cells in the testes to produce more testosterone, and FSH supports spermatogenesis. The result is endogenous testosterone elevation driven by the body's own production pathway.

Preservation of the HPG Axis

Because enclomiphene stimulates rather than replaces endogenous testosterone, LH and FSH levels rise during therapy rather than falling. Testicular function and spermatogenesis are maintained. This is the defining clinical advantage of the SERM approach: the HPG axis remains active and intact throughout treatment. A 2013 pharmacodynamic study in BJU International by Wiehle and Cunningham confirmed this in 48 men with secondary hypogonadism (baseline total testosterone <350 ng/dL, LH <12 IU/L) randomized to enclomiphene 6.25 mg, 12.5 mg, or 25 mg daily versus AndroGel 5 g daily for 6 weeks — the 25 mg enclomiphene group reached a mean total testosterone of 604 ± 160 ng/dL by day 42, with LH and FSH rising above baseline, while the transdermal testosterone group showed suppressed gonadotropins.

Dosing and Pharmacokinetics

Enclomiphene is an oral compound. In a Phase II dose-ranging study of 48 men with secondary hypogonadism, Wiehle and colleagues tested enclomiphene at 6.25 mg, 12.5 mg, and 25 mg daily for 6 weeks — all three doses increased total testosterone, with the 25 mg group reaching 604 ± 160 ng/dL versus 500 ± 278 ng/dL in the AndroGel comparator arm (p = 0.23). Pharmacokinetic data primarily from female studies suggests enclomiphene has a shorter half-life than zuclomiphene, which contributes to its cleaner pharmacokinetic profile with repeated dosing. Providers determine appropriate dosing based on individual baseline hormone values, response, and clinical presentation. Your provider will determine the appropriate dose and duration for your specific situation.

What the Research Shows About Effectiveness

Testosterone Normalization and Fertility Preservation

The strongest clinical evidence for enclomiphene comes from Phase II and Phase III randomized controlled trials. A 2016 Phase III report in BJU International by Kim and McCullough analyzed two double-blind, placebo-controlled studies (ZA-304 and ZA-305; N = 256 total) of overweight men aged 18–60 with secondary hypogonadism (baseline total testosterone ≤300 ng/dL, LH <9.4 IU/L) randomized to enclomiphene, AndroGel 1.62%, or placebo for 16 weeks — enclomiphene raised mean testosterone from ~205 ng/dL at baseline to 446 ng/dL and 413 ng/dL in the two studies (p = 0.0007 and p = 0.0368 vs. placebo), while sperm concentration increased 12–15% in the enclomiphene groups versus decreases of 33–57% in the AndroGel groups (p < 0.001). A 2014 multicenter Phase II RCT in Fertility and Sterility by Wiehle and Fontenot (NCT01270841) randomized men with secondary hypogonadism to oral enclomiphene citrate or 1% topical testosterone gel and reported that enclomiphene increased morning serum testosterone, estradiol, and LH to levels comparable with topical testosterone while raising FSH and conserving sperm counts — confirming that the SERM approach preserves the gonadotropin signaling and fertility parameters that exogenous testosterone suppresses. A 2019 open-label pharmacodynamic study in JCEM by Miller and Moore gave 12 healthy men aged 25–38 clomiphene 50 mg daily for 30 days (racemic mixture, not enclomiphene specifically) and documented a 146% increase in testosterone (SEM ±23%), a 177% increase in LH (±34%), and a 170% increase in FSH (±33%) from baseline — confirming the magnitude of HPG axis stimulation achievable with clomiphene-class SERMs.

Tolerability Compared to Clomiphene

A 2024 comparative study in Translational Andrology and Urology by Saffati and Kassab evaluated 66 hypogonadal men and found that enclomiphene produced a median testosterone increase of 166 ng/dL versus 98 ng/dL for clomiphene (p = 0.20), while lowering estradiol by 5.92 pg/mL compared to a 17.50 pg/mL increase with clomiphene (p = 0.001) — and enclomiphene carried significantly lower odds of adverse events including decreased libido, reduced energy, and mood changes (OR 0.18; 95% CI 0.07–0.44; p = 0.02). A 2023 retrospective comparison in Cureus by Thomas and colleagues analyzed 78 men (46 on enclomiphene 12.5–25 mg daily, 32 on clomiphene 50 mg every other day; median age 41–42) treated for at least 3 months and found that enclomiphene raised median LH from 3.1 to 5.5 mIU/mL (p = 0.004), FSH from 4.4 to 7.4 mIU/mL (p = 0.027), and total motile sperm count from 0.73 to 4.01 million (p = 0.039), while both compounds raised testosterone without impairing semen volume or concentration.

Enclomiphene vs. TRT and Clomiphene: Key Differences

Enclomiphene, exogenous testosterone, and racemic clomiphene all raise testosterone levels, but they differ in mechanism, fertility impact, and tolerability.

Testosterone replacement therapy (TRT) delivers exogenous testosterone directly, which suppresses the HPG axis. LH and FSH secretion drops sharply, testicular function diminishes, and sperm production falls. A 2013 literature review by Crosnoe and Grober in Translational Andrology and Urology, synthesizing 28 references from PubMed (1990–2013), established that exogenous testosterone suppresses intratesticular testosterone and is a preventable cause of male infertility — an integrated analysis of hormonal contraception studies found that 67% of men recovered sperm density above 20 million/mL within 6 months, 90% within 12 months, and 100% within 24 months after discontinuation. In the key enclomiphene RCTs, participants receiving topical testosterone showed testosterone normalization but concurrent spermatogenesis suppression — the opposite of what enclomiphene produced. For men with active fertility goals, this tradeoff is the central reason providers consider a SERM-based approach instead.

Clomiphene (racemic) contains both the enclomiphene trans-isomer and the zuclomiphene cis-isomer, which has estrogenic partial agonist activity and a long half-life. A 2017 observational study by Helo and Mahon in BJU International measured isomer levels in 15 men (median age 36, BMI 32.0) taking clomiphene 25 mg daily for a median of 25.9 months and found a zuclomiphene-to-enclomiphene serum ratio of 20:1 (median zuclomiphene 44.0 ng/mL vs. enclomiphene 2.2 ng/mL), confirming that zuclomiphene becomes the predominant circulating isomer with chronic use. This sustained estrogenic activity may explain the mood and vision side effects associated with long-term clomiphene use in men — effects that are less frequently reported with pure enclomiphene. A 2025 meta-analysis of RCTs in Archives of Endocrinology and Metabolism by Hohl and colleagues found that SERM therapy increased total testosterone by a mean of 273.76 ng/dL versus placebo (95% CI 191.87–355.66; p < 0.01) and raised LH by 4.66 IU/L and FSH by 4.59 IU/L, with no significant difference in total testosterone between SERM and testosterone gel groups. Separately, a 2022 systematic review in Andrology by Huijben and Lock pooled 19 studies (4 RCTs and 15 observational; N = 1,642; treatment duration 1.5–52 months) and found that clomiphene citrate increased total testosterone with side effects reported in fewer than 10% of participants and no serious adverse events — though clomiphene data are not directly interchangeable with enclomiphene given the known isomer differences.

Side Effects and What to Expect

Most reported adverse effects with enclomiphene are mild. The side effect profile is generally more favorable than racemic clomiphene, consistent with the absence of the zuclomiphene estrogenic component. Systematic long-term safety data remain limited given the NDA that received a Complete Response Letter.

Common side effects:

• Headache (reported in Phase II and III trials, typically mild)
• Elevated estradiol (enclomiphene drives testosterone production, which aromatizes to estradiol; providers monitor this during therapy)
• Acne or oily skin, based on testosterone therapy studies and consistent with elevated androgen activity
• Mood variability, less frequent with pure enclomiphene than with clomiphene

Less common but reported:

• Visual disturbances (reported more frequently with clomiphene than with pure enclomiphene; contact your provider promptly if visual changes occur)
• Polycythemia (elevated red blood cell count with sustained testosterone elevation; risk data derived from TRT studies and may differ for SERMs; monitored via CBC)
• Elevated PSA in older men (monitoring recommendation extrapolated from TRT data; providers assess at baseline and during therapy)

Providers monitor hormone levels, CBC, and PSA during therapy and adjust dosing based on individual response. Because enclomiphene raises endogenous testosterone, its effects on red cell production and prostate tissue may be comparable to other testosterone-elevating therapies based on TRT-derived data and require appropriate baseline and follow-up testing.

Who Is Enclomiphene Typically Prescribed For?

Secondary Hypogonadism With Fertility Goals

Enclomiphene is most commonly evaluated for men with secondary hypogonadism: low testosterone caused by insufficient LH and FSH signaling rather than primary testicular failure. In this population, the HPG axis is intact but underactive. Providers typically consider enclomiphene when a man presents with low total testosterone, low-normal or low LH and FSH, and either active fertility goals or a desire to preserve spermatogenesis. A provider will assess whether the patient has secondary versus primary hypogonadism before prescribing, as enclomiphene will not stimulate production if the testes themselves are the limiting factor.

Men Who Want Testosterone Support Without TRT Suppression

A second population consists of men with symptomatic low testosterone who want endogenous support without the HPG axis suppression associated with TRT. This includes men who have previously experienced spermatogenesis suppression on TRT, men who want to maintain testicular volume, and men who prefer to stimulate their own testosterone production rather than replace it. No FDA-approved indication exists for enclomiphene, and any prescribing represents the independent clinical judgment of the provider. Use of compounded medications that are not FDA-approved is the independent clinical judgment of the prescribing physician.

Who Should Not Take Enclomiphene

A licensed provider will evaluate individual risk factors before prescribing. The following are generally considered contraindications or conditions requiring additional clinical scrutiny:

• Primary hypogonadism (testicular failure, including Klinefelter syndrome) — enclomiphene stimulates LH and FSH but cannot compensate for absent testicular response
• Active or suspected hormone-sensitive malignancy, including prostate cancer or testicular cancer, as testosterone elevation may affect disease progression
• Severe hepatic impairment — enclomiphene is hepatically metabolized; impaired clearance may affect drug levels and tolerability
• Hypersensitivity to clomiphene or enclomiphene compounds
• Men not willing to undergo baseline and follow-up hormone and CBC monitoring, as safe prescribing requires ongoing assessment of testosterone, estradiol, and hematologic response

This is not an exhaustive list. A licensed provider will conduct a full clinical evaluation, including baseline bloodwork, before determining eligibility.

Is Enclomiphene Legal?

As of April 2026, enclomiphene is not FDA-approved for any indication. The NDA for Androxal (branded enclomiphene) received a Complete Response Letter from the FDA in 2015, citing concerns about study design adequacy and clinical benefit demonstration. The FDA recommended additional Phase 3 studies that were never completed. No other NDA or ANDA for enclomiphene has been submitted.

Enclomiphene is available only through licensed compounding pharmacies by prescription from a licensed provider. It is not available over the counter in any formulation. All prescribing represents the independent clinical judgment of the provider, not an FDA-approved indication. Enclomiphene is not available in all states; it is currently not available in New York or New Jersey. Compound reference data: PubChem CID 1548953.

What to Test Before Starting Enclomiphene

Establishing a comprehensive hormonal and safety baseline before beginning enclomiphene is essential. Enclomiphene's mechanism is HPG axis stimulation, and the markers below directly track whether that mechanism is engaged and whether the response is within a safe physiological range.

• Total testosterone: The primary outcome marker. Establishes the pre-treatment baseline against which response is measured. Low pre-treatment levels confirm hypogonadism and provide a reference point for target range discussions.
• Free testosterone: Reflects biologically active testosterone not bound to SHBG or albumin. Important in men with elevated SHBG, where total testosterone may understate the degree of deficiency.
• Luteinizing hormone (LH): Low or low-normal LH confirms secondary hypogonadism and indicates the HPG axis is the appropriate target for SERM therapy. Enclomiphene's effect should produce a measurable LH increase.
• Follicle-stimulating hormone (FSH): Assesses pituitary output and spermatogenic potential. Baseline FSH informs fertility prognosis and helps identify primary versus secondary hypogonadism.
• Estradiol: Testosterone aromatizes to estradiol. Baseline estradiol establishes pre-treatment aromatization rate and helps providers anticipate whether estradiol management will be needed during therapy.
• Sex hormone binding globulin (SHBG): Binds testosterone in circulation and reduces free fraction. Elevated SHBG depresses free testosterone disproportionately and affects how providers interpret total testosterone values.
• Prolactin: Elevated prolactin suppresses GnRH and LH secretion and is a reversible cause of secondary hypogonadism. Ruling out hyperprolactinemia before starting enclomiphene ensures the correct underlying cause is being addressed.
• Complete blood count (CBC): Establishes baseline hematocrit and red cell indices. Testosterone elevation increases erythropoiesis; monitoring CBC during therapy tracks polycythemia risk.
• PSA (prostate-specific antigen): Baseline PSA is standard before initiating any testosterone-elevating therapy in men over 40. Providers use this to identify pre-existing prostate concerns and to monitor for PSA changes during treatment.
• Comprehensive metabolic panel: Covers liver and kidney function. Relevant for hepatic metabolism of enclomiphene and for monitoring general safety during prescription compound use.

What Your Bloodwork May Show While on Enclomiphene

When enclomiphene is working as intended, the hormonal picture changes in a predictable direction. Total and free testosterone should rise toward the normal range. LH and FSH should increase, confirming that the HPG axis is responding to estrogen receptor blockade. Estradiol may rise as a consequence of increased testosterone aromatization; providers monitor this and adjust if estradiol climbs outside a clinically acceptable range. Sperm parameters, if monitored via semen analysis, should remain stable or improve. Hematocrit and hemoglobin may trend upward with sustained testosterone elevation; CBC at follow-up intervals tracks this. These changes tell a coherent story when you have a pre-treatment baseline to compare against. Without that baseline, the data is harder to interpret.

That principle, measuring first and then tracking how values respond, is central to Superpower's approach to preventive health. Every decision about hormone support should start with knowing where your biomarkers stand and continue with objective tracking of how they change.

Frequently Asked Questions

What is the difference between enclomiphene and clomiphene?

Clomiphene is a racemic mixture of two isomers: enclomiphene (trans) and zuclomiphene (cis). Enclomiphene is the active estrogen receptor antagonist that drives LH and FSH release. Zuclomiphene has estrogenic partial agonist activity and a long half-life, accumulating with chronic use. A 2017 study by Helo and Mahon measured isomer levels in 15 men taking clomiphene 25 mg daily for a median of 25.9 months and found a zuclomiphene-to-enclomiphene serum ratio of 20:1, confirming that zuclomiphene becomes the dominant circulating isomer with prolonged use. Pure enclomiphene avoids this accumulation, which may explain its more favorable tolerability profile in comparative studies.

Does enclomiphene affect fertility?

In two Phase III RCTs by Kim and McCullough of 256 overweight men aged 18–60 with secondary hypogonadism (baseline total testosterone ≤300 ng/dL), enclomiphene raised mean testosterone to 413–446 ng/dL at 16 weeks and maintained sperm concentration in the normal range — only 2–5% of enclomiphene-treated men fell below 15 million/mL, compared to 24–49% in the AndroGel 1.62% group (p < 0.001). Because enclomiphene stimulates FSH alongside LH, it supports the Sertoli cell signaling that drives sperm production. This is the primary fertility-related advantage over TRT. Individual outcomes depend on baseline sperm parameters and whether any primary testicular pathology is present.

Can enclomiphene be used long-term for testosterone?

Long-term safety data for enclomiphene specifically is limited; the FDA requested additional cardiovascular safety data before approving the NDA, and that trial data was not submitted. Clomiphene, the racemic precursor, has longer observational follow-up in men, with a 2022 systematic review in Andrology by Huijben and Lock pooling 19 studies (N = 1,642; treatment duration 1.5–52 months) and finding side effects in fewer than 10% of participants, no serious adverse events, and improvements in androgen deficiency symptoms and metabolic profiles. Providers who prescribe enclomiphene long-term typically monitor hormone levels, CBC, PSA, and liver function at regular intervals. Your provider will determine whether ongoing use is appropriate for your specific situation.

Who should not take enclomiphene?

Men with primary hypogonadism (testicular failure) are not appropriate candidates because enclomiphene requires a functional HPG axis to work. Other considerations include active hormone-sensitive malignancy, severe hepatic impairment, and hypersensitivity to clomiphene compounds. A provider will evaluate your complete clinical picture before prescribing.

How long does it take for enclomiphene to raise testosterone?

In a Phase II study by Wiehle and colleagues of 48 men with secondary hypogonadism receiving enclomiphene 6.25–25 mg daily, total testosterone increases were detected within 2 weeks, with the 25 mg group reaching 604 ± 160 ng/dL by week 6. LH and FSH typically respond within the first weeks of therapy, reflecting rapid HPG axis stimulation. Full assessment of hormonal response is generally made at the 4- to 8-week mark, when providers compare post-treatment levels to baseline. Semen analysis changes, if relevant, are evaluated over a longer timeframe, typically 3 months or more.

Is enclomiphene FDA-approved?

No. The NDA for Androxal (branded enclomiphene) received a Complete Response Letter from the FDA in 2015, citing concerns about study design and clinical benefit demonstration. Enclomiphene is not FDA-approved for any indication. It is available only through licensed compounding pharmacies by prescription. Any prescribing represents the independent clinical judgment of the provider, not an FDA-approved indication.

What blood tests should I get before starting enclomiphene?

The core pre-treatment panel includes total testosterone, free testosterone, LH, FSH, estradiol, and SHBG. These markers establish your HPG axis baseline and confirm secondary hypogonadism is the appropriate diagnosis. Prolactin rules out hyperprolactinemia as a reversible cause. PSA, CBC, and a comprehensive metabolic panel round out the safety baseline. See the testosterone, SHBG, and prolactin biomarker guide for additional context on interpreting these values.

IMPORTANT SAFETY INFORMATION

Enclomiphene is NOT FDA-approved for any indication. The NDA for Androxal received a Complete Response Letter from the FDA in 2015. Enclomiphene is available only through licensed compounding pharmacies by prescription. All prescribing represents the independent clinical judgment of your provider. Superpower connects patients with licensed providers and compounding pharmacies; Superpower does not prescribe or dispense medications.

Warnings: elevated estradiol (monitor during therapy), acne, mood variability, visual disturbances (less frequent than with racemic clomiphene; contact provider promptly), polycythemia (monitor CBC), PSA elevation in older men.

Contraindications: primary hypogonadism (testicular failure), active hormone-sensitive malignancy, severe hepatic impairment, hypersensitivity to clomiphene compounds.

Common side effects: headache, elevated estradiol, acne or oily skin, mood changes.

Not available in all states.