Hormonal, Metabolic, and Circulatory Responses to Insulin-Induced Hypoglycemia in Pregnant and Nonpregnant Women with Insulin-Dependent Diabetes

ABSTRACT

Strict blood glucose control of pregnant women with insulin-dependent diabetes is associated with increased risk of hypoglycemia. The hormonal and circulatory responses to an acute episode of insulin-induced hypoglycemia were studied in eight pregestational and one gestational diabetic women during the last trimester of pregnancy and 8 to 12 weeks postpartum. Following an overnight fast, insulin was injected intravenously (0.1 to 0.2 IU insulin/kg). Blood samples were taken at -15, 0, 15, 30, 40, 60, 90, and 120 minutes for analyses of metabolites (glucose, nonesterified fatty acid (NEFA), glycerol, 3-hydroxybutyrate) and counterregulatory hormones (epinephrine, norepinephrine, glucagon, and cortisol). Placental scintigraphy (indium-113m) was performed in five pregnant patients before and during hypoglycemia. Both during pregnancy and postpartum, blood glucose decreased to the same low level (3.2 mmol/L) concomitantly with significant decreases in NEFA, glycerol, and 3-hydroxybutyrate. Epinephrine and norepinephrine showed significant and similar increases on both occasions in relation to hypoglycemia, although there was no response in glucagon and cortisol concentrations. Maternal heart rate was significantly higher in the pregnant compared with the nonpregnant state and increased significantly in both groups in response to hypoglycemia. Placental blood flow showed no consistent changes and was unrelated to the glucose and catecholamine responses. Fetal heart rate remained unchanged. Thus, it seems as if hormonal and circulatory responses to acute hypoglycemia are not altered in diabetic women during pregnancy.