EFFECTS OF OESTROGENS ON PROLACTIN AND THYROTROPHIN RESPONSES TO TRH IN WOMEN DURING THE MENSTRUAL CYCLE AND UNDER ORAL CONTRACEPTIVE TREATMENT

Abstract

The effects of physiological and pharmacological variations of estrogens on prolactin and thyrotropin (TSH) secretion were studied during the menstrual cycle and under oral contraceptive treatment. Women (10) were tested for prolactin and TSH responses to 200 .mu.g TRH [TSH-releasing hormone] in the early follicular (days 4-6), periovulatory (days 14-15) and luteal phases (days 22-26) of the same menstrual cycle. Circulating plasma prolactin levels did not significantly vary in the 3 phases, but TSH basal levels were lower in the luteal than in the follicular and periovulatory periods. The prolactin response to TRH was significantly enhanced in the periovulatory phase, while the TSH response was slightly decreased. Women (7) on sequential contraceptives exhibited increased basal and TRH-induced prolactin secretion during estrogen treatment, with an unaltered TSH secretion throughout therapy. Treatment with combined contraceptives did not alter either basal or TRH-induced prolactin secretion in 8 women, but basal TSH secretion and its response to TRH were both reduced. Estrogens may produce different regulatory effects on prolactin and TSH secretion, particularly in the pituitary sensitivity to TRH stimulation. Physiological variations of estrogen secretion such as those observed during the menstrual cycle can likewise modify prolactin levels. These results could provide some support for a regulatory role for prolactin in the menstrual cycle.