Prolactin production by human endometrium during the normal menstrual cycle

Prolactin (PRL) synthesis by human decidua from term pregnancies has been reported. The present study examined the tissue content and in vitro production of prolactin by “decidualized” and “nondecidualized” endometrium unassociated with pregnancy. Tissue obtained throughout the menstrual cycle was dated histologically. When proliferative endometrium (N = 16) or secretory endometrium prior to day 22 (N = 6) was examined, no PRL was detected in the tissue or medium after a 24-hour incubation at 37°C in Gey s buffer. Total PRL in tissue and medium measured by radioimmunoassay increased significantly from 1.2 ± 0.3 ng/100 mg of tissue at cycle days 22 to 24 (N = 4) to 5.3 ± 2.4 ng/100 mg of tissue at cycle days 25 to 26 (N = 7). The addition of 100 μg/ml of cycloheximide to the medium prevented the net increase in PRL content during incubation. It is concluded that PRL is synthesized by endometrium during the normal menstrual cycle and that the appearance and degree of synthesis and decidualization of the stroma correspond.