Luteinising Hormone and Follicle-Stimulating Hormone
The major hormones under GnRH control are luteinising hormone (LH) and follicle-stimulating hormone (FSH) (Fig. 11.4). GnRH acts on pituitary gonadotrophs via cell-surface receptors to stimulate the release of LH and FSH by a calcium-dependent, cAMP-independent, mechanism. Diacylglycerols may amplify the calcium-mediated signal. In addition, GnRH probably has a long-term effect on LH and FSH synthesis.
The episodic secretion of GnRH into the hypophysial portal system results, in turn, in episodic secretion of LH. In adult men, the secretory pulses of LH occur at a frequency of eight to fourteen per twenty-four hours. Pulsatile secretion of FSH also occurs but with a lower amplitude.
