Maternal serum prolactin and its response to TRH in normal and complicated early pregnancy.

Maternal serum prolactin levels (PRL) were measured by radioimmunoassay in thirty-four women with either normal or complicated early pregnancy. The basal PRL level (mean +/- S.D.) of 33.4 +/- 16.4 ng/ml in normal pregnancy (n = 15) was similar to the level of 32.7 +/- 18.8 ng/ml in threatened abortion (n = 11) and 32.8 +/- 16.9 ng/ml in hyperemesis gravidarum (n = 8). Two patients, one with blighted ovum and the other with subsequent spontaneous abortion, demonstrated PRL levels lower than the range of 20-63 ng/ml in the control group. The PRL response to 200 microgram of synthetic thyrotropin releasing hormone (TRH) administered intravenously was similar throughout the patient groups. The basal level of PRL in the whole series was more closely related to the level of serum oestradiol (r = 0.778, P less than 0.001) than to that of serum progesterone (r = 0.442, P less than 0.05). However the increments of PRL following TRH administration did not correlate with either oestradiol or progesterone.