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Changes in the Prolactin Response to Thyrotropin-Releasing Hormone (TRH) During the Menstrual Cycle of Normal Women

Endocrine Division, Department of Medicine, Baylor College of Medicine, Houston, Texas 77030, Tufts University Medical School, Boston, Massachusetts, and Residencia Sanitaria "La Paz," Madrid, Spain

Serum prolactin (PRL) and thyrotropin (TSH) levels were measured after iv administration of 200µg of synthetic thyrotropin-releasing hormone (TRH) in 20 normal women ages 18 to 34. Ten women received TRH on days 7 to 8 of the menstrual cycle and 10 women received TRH on days 21–22. Although there was no difference in the dose of TRH relative to body weight in the two groups of women, the peak PRL level after TRH stimulation was greater in the women studied on day 21–22 (48.5±5.7 ng/ml, mean±SE) than on day 7–8(35.2±4.2 ng/ml) of the cycle (P<0.05). In contrast, TSH rose to a greater degree in the preovulatory phase (13.8±1.8µU/ml) than the luteal phase (7.7±0.7µU/ml of the cycle (P<.01). Studies of the PRL and TSH response after TRH administration should take the phase of the menstrual cycle into account.

Supported by Grant No. 5T32AM07039.

Received October 25, 1976.