Modulatory Effect of the Ovary on LH Secretion

Ovarian steroids are important regulators of gonadotropin secretion during the normal menstrual cycle. Estradiol is the predominant factor in the follicular phase, while progesterone plays an important role in the luteal phase. Gonadotropin surge attenuating factor (GnSAF) is a nonsteroidal ovarian substance that attenuates the endogenous LH surge in superovulated women. Attempts to purify GnSAF from various sources have provided several sequences. In human follicular fluid, GnSAF is shown to be the carboxyl terminal fragment of human serum albumin (HSA) and a molecular mass of 12.5 kDa. Preliminary data have shown the expression of the carboxyl terminal fragment of HSA in human granulosa cells. In vivo studies have provided evidence that GnSAF may participate in the control of LH response to GnRH in the context of a mechanism that facilitates the full expression of the midcycle LH surge. Further research is expected to clarify the role of GnSAF in women's physiology.