HCG — Gonadotropin / LH analog
Human chorionic gonadotropin (hCG) is a glycoprotein hormone structurally homologous to LH (luteinizing hormone), sharing the same alpha subunit and binding the LH/CG receptor (LHCGR) on testicular Leydig cells and ovarian theca cells. In men: activates Leydig cells → testosterone and estradiol production + maintains intratesticular testosterone (ITT) levels essential for spermatogenesis. Key clinical application: during TRT, exogenous testosterone suppresses LH/FSH → Leydig cells atrophy → ITT falls 95%+ → spermatogenesis impairs. hCG supplementation maintains ITT and prevents Leydig cell atrophy, preserving fertility. Also prevents testicular atrophy (volume). In women: triggers ovulation (LH surge mimic) in ART cycles; used as pregnancy support in luteal phase.
Overview
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Compound Class
Gonadotropin / LH analog
Mechanism of Action
Human chorionic gonadotropin (hCG) is a glycoprotein hormone structurally homologous to LH (luteinizing hormone), sharing the same alpha subunit and binding the LH/CG receptor (LHCGR) on testicular Leydig cells and ovarian theca cells. In men: activates Leydig cells → testosterone and estradiol production + maintains intratesticular testosterone (ITT) levels essential for spermatogenesis. Key clinical application: during TRT, exogenous testosterone suppresses LH/FSH → Leydig cells atrophy → ITT falls 95%+ → spermatogenesis impairs. hCG supplementation maintains ITT and prevents Leydig cell atrophy, preserving fertility. Also prevents testicular atrophy (volume). In women: triggers ovulation (LH surge mimic) in ART cycles; used as pregnancy support in luteal phase.
Regulatory Status
FDA-approved (Pregnyl, Novarel, Ovidrel for fertility). Compounded hCG widely used in TRT protocols. Note: FDA issued 2020 guidance restricting bulk powder compounding — pharmacy-compounded hCG still available under different regulations.
Evidence Level
High — FDA-approved for multiple indications. Decades of clinical use in reproductive medicine. Endocrine Society guidelines support as adjunct to TRT for fertility preservation.