24-hour serum levels of growth hormone, prolactin, and cortisol in pre- and postmenopausal women: the effect of combined estrogen and progestin treatment.

Objective: Our objective was to study the 24-h profiles of GH, prolactin (PRL), and cortisol concentrations in older postmenopausal and middle-aged premenopausal women, before and after estrogen-progestin treatment (EPT).

Design: The study was a randomized, placebo-controlled, double-blind trial. GH, PRL, and cortisol were sampled every 20 min for 24 h in 18 postmenopausal (aged 58-70 yr) and 17 premenopausal (aged 45-51 yr) women before and after 6 months of EPT.

Results: The mean 24-h GH (1.0 vs. 1.8 mU/liter, P = 0.033) and PRL (6.8 vs. 10.0 ng/ml, P = 0.009) concentrations were lower in postmenopausal than in premenopausal women. After EPT, the postmenopausal GH and PRL did not differ from premenopausal baseline levels. Postmenopausal mean 24-h GH (P < 0.001) and PRL (P = 0.002), daytime GH (P < 0.001) and nighttime PRL (P = 0.004) were higher during EPT compared with placebo. Cortisol levels did not differ. Premenopausal mean nighttime PRL (P = 0.026) and cortisol (P = 0.018) were higher during EPT compared with placebo. Postmenopausal PRL and premenopausal GH and PRL concentrations were higher at night than during the day. EPT did not alter this pattern.

Conclusions: Menopause was associated with decreased 24-h levels of GH and PRL, which were reversible with EPT. In contrast, cortisol levels were not affected by menopause or EPT. In middle-aged premenopausal women, the studied effects of EPT were limited to nighttime increases of PRL and cortisol.