Continuous 24-hour secretion of growth hormone during late pregnancy. A regulator of maternal metabolic adjustment?

A dramatic change in growth hormone secretion was demonstrated during the 3rd trimester of human pregnancy, when compared with the non-pregnant state. The pulsatile pattern, with intermittent high peaks, and low or undetectable levels between peaks, characteristic of normal men and non-pregnant women, was completely abolished. All the 10 pregnant women investigated had the same stable basal circulating growth hormone concentration. Values were in the range 6-10 mU/l and there was no evidence of pulsatile activity. Previously, in animal experiments, a continuous secretion of growth hormone has been shown to 'feminize' hepatic steroid metabolism, hepatic prolactin receptors, hepatic sulphatase activity and to stimulate pregnancy protein synthesis. The same biological principle could be valid also during human pregnancy and be related to maternal metabolic adjustment.