Neuroendocrine aging: Hypothalamic-pituitary-gonadal axis in women

Reproductive aging in women is characterized by degeneration of ovarian follicles. After a transition phase, the final menstrual period marks beginning of the postmenopausal period. Estrogen withdrawal in postmenopausal women results in elevated hypothalamic GnRH secretion resulting in increased gonadotropin secretion from the anterior pituitary gland. In the hypothalamus of postmenopausal women, there is an increase in kisspeptin and neurokinin B gene expression in a subpopulation of neurons known as KNDy (kisspeptin/neurokinin B/dynorphin) neurons. KNDy neurons are a site of steroid negative feedback, are regulators of pulsatile GnRH secretion and may even contribute to the generation of hot flushes.