Gonadotropins (FSH/LH): Evidence, Mechanism & Legal Status

Gonadotropins are the injectable glycoprotein hormones FSH and LH — supplied as recombinant proteins (follitropin alfa/beta, lutropin alfa) or purified human-urinary extracts (urofollitropin, menotropins / HMG) — that directly stimulate the ovary and testis.23 Unlike most compounds in this library, they are not research chemicals: they are mainstream, insurer-recognized biologics with decades of human randomized evidence. This monograph separates that established evidence from the narrower questions that remain genuinely unsettled.

This article is informational and editorial content for research and educational purposes only. It is not medical advice, not a protocol to follow, and not a sourcing guide. Gonadotropins are prescription biologics administered under specialist reproductive-endocrinology supervision with intensive monitoring; self-administration carries serious risks including OHSS, thromboembolism, and high-order multiple gestation. Dosing figures are reported strictly as seen in FDA labeling and published trials. Consult a licensed physician for any fertility decision.

What are gonadotropins and how do they work?

FSH and LH are heterodimeric glycoproteins sharing a common α-subunit with a hormone-specific β-subunit; glycosylation governs their half-life and bioactivity. Modern products fall into two lineages. Recombinant agents — follitropin alfa (Gonal-f) and beta are recombinant human FSH; lutropin alfa (Luveris) is recombinant human LH — are physico-chemically indistinguishable from endogenous hormone.2 Urinary-derived agents include urofollitropin (purified urinary FSH) and menotropins / HMG (Menopur), extracted from postmenopausal urine and standardized to 75 IU FSH plus 75 IU LH activity per vial; that "LH activity" is primarily derived from the concentrated hCG component, and hCG and LH act on the same receptor.314

Mechanistically, injected FSH binds the FSH receptor — a G-protein-coupled receptor on ovarian granulosa cells and testicular Sertoli cells — activating adenylate cyclase and a cAMP cascade that drives granulosa-cell proliferation, aromatase induction (estradiol synthesis), and selection of a dominant follicle; in men it sustains Sertoli-cell function and spermatogenesis.1511 LH, or its hCG surrogate, acts on theca cells to provide androgen precursors and is required for final maturation; a minimum serum LH is needed for optimal follicular growth, while excess LH arrests it.10

The critical subtlety is the trigger step. Exogenous FSH grows follicles but cannot supply the ovulatory LH surge — final oocyte maturation is triggered separately by hCG (a long-acting LH-receptor agonist) or, in GnRH-antagonist cycles, by a GnRH agonist that releases an endogenous surge.212 One level upstream, gonadorelin (synthetic GnRH) stimulates the pituitary to secrete the patient's own FSH and LH, an alternative for hypothalamic anovulation.22 Pharmacokinetically, a single subcutaneous 150 IU dose of follitropin alfa shows a terminal half-life of roughly 24–37 hours and bioavailability near 66–74%; because elimination half-life is about one day, maximal effect of a daily dose is not seen for 3–4 days — the basis for delayed dose-adjustment rules.45

What is the evidence by indication?

Gonadotropins carry the deepest evidence base in reproductive medicine. The table below grades each indication; most reach Grade A on randomized human data.

For ovulation induction, gonadotropins achieve ovulation in roughly 75–80% of cycles with per-cycle pregnancy rates around 20–25%.15 In a large prospective randomized trial of 1,387 clomiphene-resistant PCOS women, continuous rFSH gave the highest ovulation rate (89.9%) versus letrozole (79.3%) and combination therapy (57.0%), though pregnancy rates were comparable and rFSH carried higher cost and stimulation intensity.7 From a root-cause vantage, oral agents such as letrozole and addressing insulin resistance are first-line in PCOS; injectable gonadotropins are a more powerful but higher-risk second-line tool, favoring low-dose step-up protocols to limit multiples and OHSS.23

For IVF stimulation the evidence is deepest. The Cochrane review of 42 RCTs found no difference in live birth or OHSS for recombinant versus urinary gonadotropins overall, with a small but significant live-birth advantage for HMG over rFSH in some protocols and no difference versus purified urinary FSH — concluding that all gonadotropins are essentially equally effective and safe, so choice should rest on availability, convenience, and cost.1 A separate meta-analysis of 7 RCTs (2,159 women) in long down-regulation found HMG gave roughly a 4% absolute higher live-birth rate (RR 1.18, 95% CI 1.02–1.38).6 The IVF-stimulation evidence base is so large that the question is no longer whether gonadotropins work but which preparation marginally edges another; readers can browse the underlying randomized record at ClinicalTrials.gov.

In men, FSH is the primary hormone driving spermatogenesis. GONAL-f is FDA-approved for spermatogenesis induction in hypogonadotropic men (with hCG), established in 3 open-label non-randomized trials in 76 azoospermic men, with onset ranging 2.7–18 months — Grade B because the trials were non-randomized.2 For idiopathic male infertility, a meta-analysis found FSH improved spontaneous pregnancy rate (OR ~4.5) but with a high number-needed-to-treat of about 10–18 men per additional pregnancy, concentrating in low-baseline-count men — a real but unspectacular, off-label use.8 Finally, in profoundly LH-deficient women, a double-blind RCT showed significantly higher optimal follicular development with lutropin alfa plus follitropin alfa versus placebo plus FSH, validating that some patients need exogenous LH, not FSH alone.9

How safe are gonadotropins, and what doses appear in the literature?

The signature complication is ovarian hyperstimulation syndrome. Moderate-to-severe OHSS occurs in roughly 1–5% of IVF cycles, rising toward 20% in high-risk patients; US data recorded 11,562 OHSS hospitalizations from 2002–2011 with about 4.4% life-threatening events.12 Severe OHSS sharply raises venous thromboembolism — about 16.8 events per 1,000 women with OHSS versus 0.8 per 1,000 in OHSS-free IVF pregnancies — so thromboprophylaxis is advised through at least the first trimester in severe cases.12 Grade A mitigation exists: an antagonist-protocol RCT (n=1,050) reduced severe OHSS from 8.9% to 5.1% with a GnRH-agonist trigger and equal live births.13 Multiple gestation is the other major risk, occurring in about 20% of ovulation-induction live births and 35.1% in ART in GONAL-f trials — the rationale for low-dose protocols and single-embryo transfer.2 Common adverse reactions include ovarian cysts, headache, abdominal pain, nausea, and, in men, acne and gynecomastia; rare events include ovarian torsion and ectopic pregnancy.221 Contraindications include primary ovarian or testicular failure, uncontrolled thyroid/adrenal dysfunction, sex-hormone-dependent tumors, and pregnancy.3

Dosing is reported strictly as information from FDA labeling, not as a protocol. The modern route is subcutaneous. For ovulation induction, low-dose step-up regimens start around 37.5–75 IU FSH per day, titrated by ultrasound and estradiol toward a single dominant follicle.15 For IVF, the Menopur label cites 225 IU daily from cycle day 2–3, individualized after five days, to a maximum of 450 IU/day for no more than 20 days.3 For severe LH/FSH deficiency, the pivotal RCT used lutropin alfa about 75 IU/day plus follitropin alfa.9 For male spermatogenesis, GONAL-f labeling pairs FSH 150 IU three times weekly (up to 300 IU) with hCG, continued at the lowest effective dose.2 Because the terminal half-life is about one day, dose effects plateau only after 3–4 days — hence the label's adjust-after-five-days rule.5

What is the FDA and WADA status in 2026?

Gonadotropins are FDA-approved prescription biologics with long histories — menotropins' initial US approval was in 1975, follitropin alfa in 1997. Under the Biologics Price Competition and Innovation Act, on March 23, 2020 approved gonadotropin applications were deemed biologics-license applications and transitioned from the drug (Orange Book) pathway to the biologics (PHS Act / Purple Book) pathway.1617 Consequently menotropins, urofollitropin/FSH, and hCG were removed from the 503B bulk list and are NOT eligible for 503A or 503B compounding — biologics cannot be compounded under the FD&C Act exemptions.16 This sharply distinguishes gonadotropins from gray-market research-chemical peptides: there is no legitimate research-use-only lane, and post-2020 several compounding pharmacies stopped supplying hCG/FSH precisely because of this transition.18

For anti-doping, the 2026 WADA Prohibited List (in force January 1, 2026) prohibits luteinizing hormone and human chorionic gonadotropin in MALES only under Section S2.3, because they raise endogenous testosterone, and prohibits gonadotropin-releasing factors such as GnRH agonists and gonadorelin for their indirect androgenic effect.1920 Exogenous FSH is not listed as an ergogenic-prohibited substance, since it does not raise testosterone, and gonadotropins are not relevant doping agents in women; athletes with a legitimate medical need for a prohibited agent must obtain a Therapeutic Use Exemption.19 Gonadotropins are not DEA-controlled substances.

Bottom line. Gonadotropins are the gold-standard, FDA-approved, RCT-validated injectable hormones of reproductive medicine — genuinely proven, not hyped. Grade A evidence supports ovulation induction, ART stimulation, recombinant-LH rescue of LH-deficient women, and a modest pregnancy benefit in selected idiopathic male infertility, with Grade B for spermatogenesis induction. They are legally unambiguous approved biologics, not compoundable research chemicals — a clean contrast to most peptides in this library. The real-world caveats are clinical: OHSS and multiple gestation are the dose-dependent dangers, mitigated by low-dose protocols, antagonist cycles, agonist triggering, and single-embryo transfer. Regulatory facts here are current as of June 2026 and should be re-verified against the live FDA and WADA records.