Negative Feedback Effects of Gonadal Steroids Are Preserved with Aging in Postmenopausal Women

Abstract

There is now evidence for alterations in the neuroendocrine control of the reproductive axis with aging, but its sensitivity to gonadal steroid negative feedback remains controversial. To examine the independent effect of age and gonadal steroid negative feedback, younger (45–55 yr; n = 7) and older (70–80 yr; n = 6) postmenopausal women (PMW) were studied at baseline on no HRT, after 1 month of transdermal estrogen (50 μg/d; E) and again after a further month of E and 7 d of transvaginal progesterone (P) (100 mg bid; E + P). At each admission, blood was sampled every 5 min for 8 h for measurement of gonadotropin free α-subunit (FAS), which was used as a marker of GnRH pulse frequency. LH and FSH were measured in pooled samples.