24-Hour Serum Levels of Growth Hormone, Prolactin, and Cortisol in Pre- and Postmenopausal Women: The Effect of Combined Estrogen and Progestin Treatment

Abstract

Previous studies of the effects of hormone therapy (HT) on levels of growth hormone (GH), prolactin (PRL), and cortisol have yielded conflicting results. The present study analyzed 24-hour profiles of these hormones before and after estrogen/progestin treatment (EPT) in 17 healthy premenopausal women 45 to 51 years of age and 18 postmenopausal women 58 to 70 years of age. Using a randomized, placebo-controlled, double-blind design, hormone levels were sampled at 20-minute intervals for 24 hours, before and after 6 months of EPT. Premenopausal women received cyclic EPT with 2 mg of estradiol valerate for 16 days, followed by estradiol plus 1 mg of norethisterone acetate (NETA) for 12 days. Postmenopausal women received continuous EPT with 2 mg of estradiol valerate plus 0.7 mg of NETA. Some women in each of these groups received placebo. Mean 24-hour levels of both GH and PRL were lower in postmenopausal than in premenopausal women. Average serum concentrations were 1.0 versus 1.8 mU/L, respectively, for 24-hour GH, and 6.8 versus 10.0 ng/ml for PRL. No such difference was found for either GH or PRL following EPT, at which time baseline hormone levels were comparable in pre and postmenopausal women. Mean postmenopausal 24-hour levels of GH and PRL were higher during EPT than in control subjects, as were daytime GH levels and nighttime PRL concentrations. No differences in serum cortisol were observed. In premenopausal women, mean nighttime PRL and cortisol levels were higher during EPT than in placebo recipients. Postmenopausal PRL levels and premenopausal levels of GH and PRL were higher at night than during the day, whether or not subjects were receiving EPT.