Metabolic changes in gestational diabetes

Abstract

Normal pregnancy produces profound metabolic alterations that occur, in large part, by the conclusion of the first trimester. Although necessary to support the metabolic needs of the conceptus, the metabolic and cardiovascular changes of pregnancy are well established weeks before the metabolic needs of the fetus and placenta are fully expressed. The endocrine and metabolic characteristics of gestational diabetes, therefore, can only be understood against the backdrop of the rapidly changing conditions of normal pregnancy. Nondiabetic pregnancy produces an "accelerated starvation" in the fasting state with an earlier and more profound hypoglycemia and an increased fasting insulin. In the fed state, normal pregnancy produces a higher postprandial glycemic response despite an amplified first phase insulin response and higher plasma insulin concentrations. Both the intravenous glucose tolerance test and the steady state euglycemic clamp demonstrate that, by the second trimester, pregnancy produces peripheral and, perhaps, hepatic insulin resistance. The decreased peripheral uptake of glucose and the increased basal production of glucose in the fasting state support an increased flux of glucose to the fetus. Weight-matched obese gestational diabetic gravidae demonstrate a greater fall in fasting glucose and greater increase in ketosis compared with normal control gravidae. Obese GDM patients appear to have increased fasting insulin concentration compared with lean GDM and nondiabetic controls, whereas nonobese GDM patients do not appear to have elevated fasting insulin concentrations. Women with gestational diabetes have a greater rise in SI postpartum than controls, though the SI is the same in normal and gestational diabetic pregnancy in the third trimester.(ABSTRACT TRUNCATED AT 250 WORDS)