Estrogen replacement therapy increases prolactin levels in postmenopausal women

Objective: Numerous studies have focused on the secretion of follicle-stimulating hormone (FSH), luteinizing hormone (LK), and estradiol-17 beta in menopausal women, as well as the effect of hormone replacement therapy (HRT) on pituitary hormone secretion. However, data on prolactin (PRL,) concentrations in postmenopausal women still are scarce. In the present study, the authors analyzed the effect of various doses of estrogen administration on PRL serum levels in 120 postmenopausal women who received three monthly courses of HRT. Design: The patients were assigned randomly into three treatment groups of 40 subjects each; one group received 0.320 mg, another received 0.624 mg, and the third group received 1.25 mg of conjugated estrogens administered by mouth daily for 21 days. Baseline PRL levels were lower [5.3 +/- 1.4 ng/ml (mean +/- standard deviation)] than those observed in healthy menstruating women studied during the follicular phase of the cycle (11.2 +/- 3.4 ng/ml). Results: Three courses of HRT enhanced significantly (p < 0.001) PRL levels up to 12.6 +/- 7.1 ng/ml, and this increment was related to the dose of conjugated estrogens. Serum levels of estradiol-17 beta (estradiol) also exhibited a linear correlation (r = 0.40) with PRL concentrations at the term of the study. Conclusions: From these results, the authors concluded that HRT exerts a stimulating effect on PRL secretion, but the significance of this response remains to be seen because variations in PRL concentrations during menopause have not been analyzed closely.