Prolactin response to thyrotropin-releasing hormone in normal and complicated late pregnancies.

Maternal serum prolactin level (PRL) was determined with radioimmunoassay in normal and complicated late pregnancy. The mean basal PRL levels were not statistically different among normal (179.3 ng/ml), preeclamptic (169.7 ng/ml), hypertensive (171.4 ng/ml), twin (194.8 ng/ml), or diabetic pregnancies (134.4 ng/ml), although 3 of 17 diabetic women had abnormally low PRL levels. The PRL response to 200 micrograms of intravenously administered thyrotropin-releasing hormone (TRH) was investigated and found similar in normal, preeclamptic, hypertensive, and twin pregnancies. There was no response to TRH in 2 of 3 diabetics with a low basal PRL level. One of these diabetic patients experienced an unexplained intrauterine death 4 weeks later; the others delivered term infants, 1 of whom died of respiratory distress syndrome (RDS). These preliminary results suggest that low basal PRL levels and unresponsiveness to TRH may be related to a poor fetal or neonatal prognosis in diabetic pregnancies.