Current concepts on ultradian rhythms of luteinizing hormone secretion in the human.

A cardinal physiological feature of anterior pituitary hormone secretion is its pulsatile mode of signalling to remote target tissues. The pulsatile release of anterior pituitary hormones is orchestrated by episodic neuronal activation of hypothalamic control centres, which release relevant effector molecules intermittently. The anterior pituitary gland in turn secretes hormones in ultradian bursts, and thereby communicates with and governs the function of peripheral target organs. In the case of the reproductive axis, the release of gonadotrophin-releasing hormone (GnRH) from the hypothalamus in intermittent secretory bursts is a primary neural determinant of pulsatile gonadotrophin [luteinizing hormone (LH) and follicle stimulating hormone (FSH)] secretion. In men, women and pubertal children, the pulsatile mode of GnRH release is critical for sustained physiological function of gonadotroph cells and is an absolute prerequisite for reproductive capability. Furthermore, various clinical pathophysiological states, such as inadequate nutrient intake, stress and uraemia, may dramatically impair the pulsatile release of gonadotrophic hormones. Here, we review some recent studies in reproductive (neuro)endocrinology that illustrate physiological regulation and pathophysiological disruption of pulsatile LH signalling in the human.