Relative Effects of Pregnancy, Human Placental Lactogen and Prednisolone on Carbohydrate Tolerance in Normal and Subclinical Diabetic Subjects

Abstract

Six subclinical diabetic postpartum women with normal standard glucose tolerance tests (GTT) but diabetic responses during prednisolone glucose tolerance tests (PGTT) had a third GTT performed after an overnight infusion of human placental lactogen (HPL). Similar studies were done on six control postpartum women with normal GTT and PGTT. HPL infusions produced plasma levels of the hormone that were comparable to concentrations observed in late pregnancy. In the control group HPL infusion had minimal effects on GTT, and no significant changes of plasma immunoreactive insulin (IRI) were observed. Higher, though normal, glucose levels during PGTT were associated with corresponding elevations of IRI. HPL infusion, like prednisolone administration, induced diabetic curves in the subclinical diabetic subjects, and IRI levels did not rise significantly above corresponding GTT levels until the second hour even though abnormal hyperglycemia was established between one-half and one hour. Both hormones increased fasting plasma glucose levels, but only prednisolone elevated fasting levels of nonesterified fatty acids. Three control and three diabetic women were also studied prepartum. Neither pregnancy nor postpartum HPL infusion altered GTT in the normal group. HPL administration to the diabetic subjects induced deterioration of carbohydrate tolerance that was more pronounced than that observed prepartum. In both groups plasma IRI was higher during prepartum testing. These observations suggest that normal women resist degrees of diabetogenic stress that produce abnormal GTT in subclinical diabetic patients. The latter group tolerated pregnancy better than postpartum HPL or prednisolone administration presumably because of the greater adaptive hyperinsulinemia that occurred during gestation.