Hypothalamic control of gonadotropin secretion

Abstract

Publisher Summary This chapter discusses the hypothalamic control of gonadotropin secretion. The control of gonadotropin secretion is extremely complex as revealed by the research of the past 40 years since the discovery of luteinizing hormone releasing hormone (LHRH), commonly called gonadotropin-releasing hormone (GnRH). This was the second of the hypothalamic-releasing hormones characterized. It stimulates follicle-stimulating hormone (FSH) release, albeit in smaller amounts than luteinizing hormone (LH). For this reason, it was renamed GnRH. Overwhelming evidence indicates that there is a separate follicle-stimulating hormone releasing hormone (FSHRH) because pulsatile release of LH and FSH can be dissociated. In the castrated male rat, roughly half of the FSH pulses occur in the absence of LH pulses, and only a small fraction of the pulses of both gonadotropins are coincident. The hypothalamic areas controlling LH and FSH are separable. Stimulation in the dorsal medial anterior hypothalamic area causes selective FSH release, whereas lesions in this area selectively suppress the pulses of FSH and not LH. Conversely, stimulations or lesions in the medial preoptic region can augment or suppress LH release respectively without affecting FSH release. The putative FSHRH is synthesized in neurons with perikarya in the dorsal anterior hypothalamic area with axons that project to the mid and caudal median eminence to control FSH release selectively.