The role of estrogen in the TSH and prolactin responses to thyrotropin-releasing hormone in postmenopausal as compared to premenopausal women.

The basal and TRH (Thyrotropin-Releasing Hormone) stimulated TSH (Thyrotropin) and PRL (Prolactin) responses (incremental area; IA) to 200 micrograms TRH was studied in 13 pre- and 13 postmenopausal women of 60 years of age. Both groups consisted of healthy women, none had goiter and all were negative for thyroid autoantibodies. The serum levels of TSH, T3, T4 and SHBG (sex hormone-binding globuline) were in the normal range and did not differ significantly between the groups. There were no differences in basal TSH (1.3 +/- 0.5 vs 1.4 +/- 0.5 mIU/l) or PRL (6.4 +/- 2.7 vs 6.6 +/- 2.5 micrograms/l) or for PRL IA (498 +/- 126 vs 584 +/- 165) between pre- and postmenopausal women. However, for TSH IA there was a slight decrease (15%), but not significant, in the postmenopausal group compared to the premenopausal group (1630 +/- 598 vs 2067 +/- 893). In conclusion, a weak but not significant decrease in the TSH response to TRH in postmenopausal women may be explained by the lower endogenous estradiol level.