Gonadorelin — Gonadotropin-releasing hormone (GnRH) — endogenous hypothalamic decapeptide; pulsatile administration stimulates LH/FSH; used in TRT to preserve testicular function and fertility
Gonadorelin is synthetic GnRH (identical sequence to endogenous hypothalamic GnRH: Glp-His-Trp-Ser-Tyr-Gly-Leu-Arg-Pro-Gly-NH2). It acts on GnRH receptors (GnRH-R) in the anterior pituitary. CRITICAL: mode of administration determines effect: (1) PULSATILE administration (subcutaneous bolus 1–2x daily or every 2 hours via pump) — mimics normal hypothalamic GnRH pulse pattern → stimulates LH and FSH secretion → testicular testosterone and spermatogenesis; (2) CONTINUOUS/prolonged exposure — causes GnRH receptor downregulation → pituitary desensitization → LH/FSH suppression → testosterone suppression (this is the mechanism used by GnRH agonists like leuprolide for prostate cancer). For TRT fertility preservation: when testosterone is administered exogenously, it suppresses the HPG axis (LH→0) via feedback, causing testicular atrophy and azoospermia. Gonadorelin (pulsatile) replaces the missing hypothalamic GnRH signal, stimulates pituitary LH release, and maintains Leydig cell function and spermatogenesis even on TRT. DISTINCTION from hCG: hCG acts at the testicular level (directly stimulates LHCGR on Leydig cells), while gonadorelin acts at the pituitary level. Gonadorelin therefore also maintains FSH (important for Sertoli cells and sperm maturation) — hCG does NOT stimulate FSH.
Overview
This page is part of Hormonaly's evidence-graded compound library. All clinical claims are linked to peer-reviewed sources via our dual-layer citation verification pipeline.
Compound Class
Gonadotropin-releasing hormone (GnRH) — endogenous hypothalamic decapeptide; pulsatile administration stimulates LH/FSH; used in TRT to preserve testicular function and fertility
Mechanism of Action
Gonadorelin is synthetic GnRH (identical sequence to endogenous hypothalamic GnRH: Glp-His-Trp-Ser-Tyr-Gly-Leu-Arg-Pro-Gly-NH2). It acts on GnRH receptors (GnRH-R) in the anterior pituitary. CRITICAL: mode of administration determines effect: (1) PULSATILE administration (subcutaneous bolus 1–2x daily or every 2 hours via pump) — mimics normal hypothalamic GnRH pulse pattern → stimulates LH and FSH secretion → testicular testosterone and spermatogenesis; (2) CONTINUOUS/prolonged exposure — causes GnRH receptor downregulation → pituitary desensitization → LH/FSH suppression → testosterone suppression (this is the mechanism used by GnRH agonists like leuprolide for prostate cancer). For TRT fertility preservation: when testosterone is administered exogenously, it suppresses the HPG axis (LH→0) via feedback, causing testicular atrophy and azoospermia. Gonadorelin (pulsatile) replaces the missing hypothalamic GnRH signal, stimulates pituitary LH release, and maintains Leydig cell function and spermatogenesis even on TRT. DISTINCTION from hCG: hCG acts at the testicular level (directly stimulates LHCGR on Leydig cells), while gonadorelin acts at the pituitary level. Gonadorelin therefore also maintains FSH (important for Sertoli cells and sperm maturation) — hCG does NOT stimulate FSH.
Regulatory Status
FDA APPROVED for hypothalamic amenorrhea and HH via pulsatile pump (Lutrepulse). Bulk compounded gonadorelin widely used in TRT practices (off-label). In 2020, FDA restricted bulk compounding of hCG; gonadorelin became the preferred compounded alternative for TRT fertility preservation.
Evidence Level
B — FDA-approved for hypothalamic amenorrhea and HH (Leydig 1982 NEJM pulsatile protocol). Off-label TRT: Observational data from hormone optimization clinics; Wenker 2015 (gonadorelin vs hCG for fertility preservation on TRT); Growing practice evidence but no large Phase 3 RCTs for off-label TRT use specifically.