Serum prolactin patterns in early human gestation.

The relation between levels of human prolactin (HPRL), other protein hromones, and estradiol in serum immediately prior to and for the first weeks after conception was determined. HPRL was measured by radioimmunoassay in serum samples obtained daily from these women during the menstrual cycle in which conception took place and for several weeks therafter. It was found that the concentration of HPRL initally increased above nonpregnant levels 32 to 36 days after the luteinizing hormone (LH) peak. The patterns of estradiol and HPRL were similar in early gestation, while there was no similarity between the patterns of HPRL and human placental lactogen. These results are in aggreement with other studies showing that high levels of estrogen influence HPRL secretion in the human subject.