The gonadotrophin surge in humans: its mechanism and role in ovulatory function--a review.

The presence of the positive feedback by oestrogen resulting in the mid-cycle gonadotrophin surge in women distinguishes the female's feedback control of gonadotrophin secretion from that in males. The gonadotrophin surge is an event crucial for final oocyte maturation, ovulation and subsequently for corpus luteum function. In this article, the roles of oestrogen, progesterone and testosterone in the regulation of the gonadotrophin surge are reviewed. Evidences appear to support the suggestion that an oestradiol pulse of sufficient potency and lasting for an adequately long duration alone is sufficient to trigger off the LH surge. Progesterone has a biphasic effect on LH secretion, and although not required for the initiation of the LH surge, may play a role in maintaining the LH peak. Testosterone, on the other hand, does not modulate the LH surge mechanism in man. Dysfunction of the gonadotrophin surge mechanism may account for some forms of ovulatory disorders: amenorrhoea and in some cases of delayed or precocious puberty. In patients with polycystic ovary syndrome (PCOS), different degrees of dysfunction of the gonadotrophin surge mechanism have been shown.