GnRHpulsen

GnRHpulsen refers to the pulsatile secretion pattern of gonadotropin-releasing hormone (GnRH) from the hypothalamus, which regulates pituitary gonadotropin release.

Physiology: GnRH is produced by hypothalamic neurons and released into the hypophyseal portal system in discrete pulses. Each pulse stimulates the anterior pituitary gonadotrophs to secrete the gonadotropins LH and FSH and to synthesize their subunits. The frequency and amplitude of pulses determine the relative output: faster pulse frequencies favor LH secretion, slower frequencies favor FSH; sustained high-frequency stimulation can preferentially increase LH relative to FSH. Continuous exposure to GnRH or GnRH agonists desensitizes receptors, suppressing gonadotropin release.

Regulation: Pulse generation is controlled by a network including kisspeptin, neurokinin B, and dynorphin neurons in the hypothalamus; feedback from sex steroids modulates pulse frequency and amplitude.

Clinical relevance: Abnormal GnRH pulsatility is linked to reproductive disorders. Pulsatile GnRH therapy is used to induce ovulation in women with hypothalamic amenorrhea or gonadotropic deficiency. In contrast, continuous GnRH agonist therapy suppresses the hypothalamic-pituitary-gonadal axis, used for conditions such as endometriosis, prostate cancer, and precocious puberty.

Measurement: GnRH cannot be easily measured in peripheral blood due to rapid clearance; LH and FSH pulsatility in plasma serve as surrogate markers of GnRH pulsatility. Research often relies on frequent sampling and specialized assays to study pulsatile patterns.