GONADOTROPIN PULSATIONS ACROSS DEVELOPMENT

Initiation and maintenance of the reproductive axis in the human is co ntingent upon the pulsatile secretion of gonadotropin-releasing hormon e (GnRH) from the hypothalamus. In man, tracking endogenous GnRH secre tion relies on frequent peripheral sampling of three glycoprotein prod ucts of the gonadotrope, luteinizing hormone (LH), follicle-stimulatin g hormone (FSH) and free cr-subunit (FAS). FAS is superior to LH as a surrogate marker of GnRH secretory dynamics in those circumstances whe re GnRH secretion is rapid or where the pituitary LH response is low, The pattern of GnRH secretion is constantly changing across developmen t; from high levels during the neonatal period, through a period of qu iescence in mid-childhood, followed by sleep-entrained reactivation of the reproductive axis at the onset of puberty, ultimately culminating in the adult pattern of pulsatile secretion which in the male is appr oximately every 2 h and in the female varies with the stage of the men strual cycle, This episodic mode of secretion allows differential impa ct of feedback mechanisms on the GnRH neurons and facilitates the main tenance of the reproductive axis during periods of stress by allowing frequency and amplitude modulations.