Age related changes in the pituitary‐testicular axis in normal men; lower serum testosterone results from decreased bioactive LH drive

Abstract

There is an underlying decline in both total-testosterone and free-testosterone index, and bioactive LH levels with advancing age, suggestive of a hypothalamo-pituitary defect which leads to lower bioactive LH levels which in turn are responsible for the diminished gonadal steroidogenesis. Elucidation of the mechanism underlying this slight decline in hypothalamopituitary testicular activity is complicated by differences between the data obtained by immunoassay or bioassay.