FSH and LH pituitary reserve and output in the postmenopause

FSH and LH basal levels and their cumulative responses following LH-RH administration were determined along with plasma estradiol levels in postmenopausal patients. 89 postmenopausal patients were studied. They were divided into four groups according to the time elapsed since their menopause. Group I being less than 2 yr postmenopausal, Group II between 2 and 5 yr, Group III 5--10 yr and Group IV 10 yr or more postmenopausal. Blood was drawn before a bolus intravenous injection of 100 micrograms of LH-RH was given and at different time intervals after the injection. FSH, LH and plasma estradiol were assayed. FSH and LH cumulative responses after LH-RH (CR) and total cumulative responses (TCR), as defined by the surface area comprised between the tracing and a horizontal line drawn through the basal level (CR) or the X-axis (TCR) were calculated by planimetry. The basal levels of FSH tend to increase with age, with a maximum in the 3rd age group and a decline thereafter. A similar trend, though less outspoken, was seen in the LH basal levels. FSH cumulative responses after LH-RH (as expressed by the mean increment (delta), maintained over the 2 h duration of the test) were significantly lower than the corresponding FSH basal levels and appeared to remain at the same level throughout postmenopause. In contrast, LH cumulative responses after LH-RH, expressed in the same way, compared with corresponding LH basal levels. They were highest in the younger age group, associated with still appreciable estradiol levels and declined in the subsequent age groups. LH-TCR and LH-TCR : FSH-TCR ratio showed a similar trend as LH cumulative responses. It is suggested that this peculiar pattern, is related to estradiol levels.