[Human growth hormone and prolactin during pregnancy (author's transl)]

In order to know the secretory behaviors of human growth hormone (hGH) and human prolactin (hPRL) during pregnancy, the following studies were undertaken. Twenty three normal pregnant women of every period of gestation, eighteen women of postpartum and five nonpregnant subjects volunteered for this study. After fasting overnight, these volunteers were placed at complete bed rest, and a fasting antecubital venous blood sample was drawn at 8:00 a.m. Then L-arginine, 30 g, was infused intravenously over a 30 minute period, and venous blood samples were drawn at 30, 45, 60, 90, 120, minutes after infusion. Serum hGH level was detected by hGH radioimmunoassay Kit (Dainabot) and serum hPRL concentration was measured by double-antibody radioimmunoassay system (NIH-NIAMDD). In addition, serum hCS level was measured by hCS-Kobe double-antibody radioimmunoassay system in comparison with the secretory behaviors of hGH and hPRL. 1. Serum hGH, hPRL and hCS concentrations during pregnancy. HGH concentration remained almost unchanged through the course of pregnancy, but hPRL and hCS concentrations increased with the programs of pregnancy. 2. Serum hGH and hPRL concentrations in puerperium. HGH level did not change as compared to that of nonpregnant or pregnant women. HPRL concentration maintained high level in 1-3 postpartum weeks. 3. Effect of arginine on the concentrations of serum hGH, hPRL and hCS during pregnancy. The hGH response decreased, but that of hPRL increased along with the progress of pregnancy. During the arginine loading test there was no significant change in hCS concentration. 4. Effect of arginine on the concentrations of serum hGH and hPRL in puerperium. The HGH response was suppressed at the first week of the postpartum. The response of hPRL was lower than that of late pregnancy. To summarize, hGH and hPRL have some similar biological characters, but there was a difference in secretion pattern of the two hormones during pregnancy. Reserve function of hGH secretion was suppressed, but that of hPRL secretion increased along with the progress of pregnancy. And in the third trimester of pregnancy, the difference of the secretory behavior and secretory reserve function between hGH and hPRL was prominent.