Inhibin and reproductive aging in women.

The monotropic FSH rise is the sentinel endocrine event that first indicates a woman is approaching the end of her reproductive potential. While a deficiency in inhibin has long been postulated as the immediate cause of the monotropic FSH rise, this has only recently been demonstrated to actually occur. It is our current hypothesis that when the number of preantral follicles in both ovaries drop below a threshold, then there is a subtle decrease in inhibin B which leads to the monotropic FSH rise which, in turn, accelerates follicular depletion and the attainment of the menopause.