GnRHn

GnRHn, short for gonadotropin-releasing hormone neurons, are a discrete group of hypothalamic neurons that synthesize and secrete GnRH, the decapeptide that governs the anterior pituitary production of luteinizing hormone (LH) and follicle-stimulating hormone (FSH). In mammals, GnRHn originate in the olfactory placode during development and migrate into the basal forebrain, where they populate the preoptic and arcuate regions and project to the median eminence.

GnRHn release GnRH in pulsatile bursts into the hypothalamic-pituitary portal circulation. GnRH binds GnRHR on pituitary gonadotrophs, stimulating synthesis, storage, and pulsatile secretion of LH and FSH. The pattern of GnRH secretion—its frequency and amplitude—helps determine the relative release of LH versus FSH, and the overall activity of the gonadotropic axis. Puberty involves an increase in GnRH pulse frequency and amplitude, enabling sustained gonadotropin secretion and gonadal maturation. Continuous exposure to GnRH, in contrast, suppresses gonadotropin release via receptor desensitization.

GnRHn activity is tightly regulated by neural networks and hormonal feedback. Kisspeptin-producing neurons, along with neurokinin B and dynorphin (the KNDy system), strongly influence GnRHn firing. Steroid hormones such as estradiol and testosterone provide positive or negative feedback, shaping pulsatility across the menstrual or estrous cycle. Other factors including sleep, stress, and metabolic state modulate GnRHn activity as part of broader homeostatic regulation.

Clinically, disruptions of GnRHn function can cause hypogonadism and infertility. GnRH analogs—agonists or antagonists—are widely used in fertility treatment and in managing hormone-sensitive cancers. In diagnostics, GnRH stimulation tests assess pituitary responsiveness and gonadotroph function.