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HPG Axis & Reproductive

Enclomiphene

Oral SERM that restarts the body's own testosterone production by raising LH and FSH, while preserving fertility, unlike TRT.

InvestigationalEvidence level 4 of 5: Human RCTs or approved abroadAlso: Enclomiphene citrate, trans-Clomiphene, Androxal

Overview

Enclomiphene is the trans-isomer of clomiphene, separated from the longer-acting, more estrogenic zuclomiphene isomer. It blocks estrogen receptors in the hypothalamus and pituitary, so the brain senses less estrogen feedback and increases GnRH, LH and FSH. The testes respond by making more testosterone and sperm. In randomized trials of overweight men with secondary hypogonadism, enclomiphene restored testosterone into the normal range while maintaining sperm concentration, whereas topical testosterone suppressed it. It is useful for men who want to preserve fertility, and as post-cycle therapy after anabolic use. It does not work in primary testicular failure. It is not FDA-approved as its own product but can be compounded under current FDA policy.

Classification
Selective estrogen receptor modulator (SERM); trans-isomer of clomiphene — small molecule
Route
Oral
Half-life
~10 hours (oral)

Mechanism of action

Primary targetEstrogen receptors in hypothalamus and pituitary
  1. Hypothalamic ER antagonismBlocks estrogen receptors that normally signal 'enough hormone' to the brain.
  2. GnRH pulse increaseHypothalamus increases GnRH pulse frequency and amplitude.
  3. LH and FSH risePituitary releases more LH and FSH into circulation.
  4. Leydig cell stimulationLH drives testicular testosterone synthesis.
  5. Sertoli cell supportFSH plus intratesticular testosterone sustain spermatogenesis.
Downstream effects
  • Higher endogenous testosterone
  • Preserved sperm production
  • Improved libido and energy

Researched for

  • Secondary (hypogonadotropic) hypogonadism
  • Male fertility preservation
  • Post-cycle HPG recovery
  • Obesity-related low testosterone

Research notes

  • Phase 3 trials (ZA-301/ZA-302; Wiehle, Kaminetsky et al.) restored testosterone to normal in most men while preserving sperm concentration versus topical testosterone.
  • FDA did not approve the NDA in 2015, citing trial design questions about endpoints; this was a regulatory, not primarily safety, decision.
  • Testosterone rises typically 1.5–2x baseline within 2–4 weeks; estradiol can rise in parallel.
  • Not effective in primary hypogonadism (testicular failure), where LH is already high.
  • Long-term cardiovascular, ocular and bone outcomes have not been established.

Reported side effects

  • Headache
  • Mood changes or irritability
  • Mild nausea
  • Estradiol elevation; gynecomastia if unmonitored
  • Visual disturbances (rare, dose-dependent) — stop if they occur

Contraindications & cautions

  • Primary hypogonadism (testicular failure)
  • History of venous thromboembolism
  • Uncontrolled pituitary or adrenal disease; prolactinoma
  • Pre-existing visual disorders
  • Liver disease

Lab monitoring

  • Total and free testosterone
  • Estradiol (sensitive assay)
  • LH, FSH, SHBG, prolactin
  • PSA (men >40 or risk factors)
  • CBC, CMP, lipids
  • Semen analysis if fertility is a goal

Dosing and pricing for Enclomiphene

Dosing references and compound pricing are available to established patients in the secure portal after a medical evaluation.

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