Early follicular phase serum FSH as a function of age: the roles of inhibin B, inhibin A and estradiol

Abstract

This study shows that, during the early follicular phase, FSH, inhibin A and estradiol but not inhibin B increase with age. Some of the increase in inhibin A and estradiol may be the result of accelerated follicular development with increasing age. Serum inhibin B and estradiol but not inhibin A are inversely correlated with FSH between ages 40 and 50, but only inhibin B is a significant independent predictor of FSH. This supports the postulate that inhibin B is the main form of inhibin regulating FSH at this stage of the menstrual cycle. During the early follicular phase, serum levels of inhibin A are presumably too low to play a significant physiological role or are less active.