GnRH receptor (agonist)

Class

synthetic decapeptide LHRH/GnRH agonist, delivered as a biodegradable subcutaneous depot

Pathway

initial stimulation of pituitary gonadotropin (LH/FSH) release is followed by sustained receptor down-regulation with chronic dosing, suppressing gonadotropin secretion and reducing gonadal sex-hormone production to castrate levels in men (testosterone) and postmenopausal levels in women (estradiol) within 2-4 weeks

The gonadotropin-releasing hormone (GnRH) receptor sits on pituitary cells that control reproductive hormone output. Normally, the hypothalamus releases GnRH in rhythmic pulses, which stimulates the pituitary to secrete luteinizing hormone (LH) and follicle-stimulating hormone (FSH). These, in turn, signal the testes or ovaries to produce testosterone or estradiol. Synthetic GnRH agonists mimic this natural hormone but are given continuously rather than in pulses. This constant stimulation initially boosts LH and FSH release, causing a transient rise in sex hormones, but with sustained exposure the pituitary receptors become desensitized and internalized, shutting down gonadotropin secretion. The downstream effect is a marked, sustained reduction in testosterone or estradiol to levels comparable to surgical removal of the gonads or menopause. This approach is used broadly in conditions where sex hormones drive disease activity, including hormone-sensitive prostate and breast cancers, endometriosis, uterine fibroids, and certain forms of precocious puberty. Because the suppression is reversible upon stopping treatment, GnRH agonists offer a pharmacological alternative to surgical gonadectomy, with the trade-off of an initial hormone surge before suppression takes hold.