INSULIN RESPONSE TO GLUCOSE INFUSION DURING PREGNANCY. A PROSPECTIVE STUDY OF HIGH AND LOW INSULIN RESPONDERS WITH NORMAL CARBOHYDRATE TOLERANCE

Abstract

ABSTRACT A decreased insulin response to glucose administration has been suggested to be a prerequisite for the development of diabetes mellitus. Factors that increase the demand for insulin in the organism may precipitate diabetes in subjects with a low insulin response to a glucose infusion test (GIT). Since it is well-known that pregnancy is a diabetogenic factor, its effect on the carbohydrate metabolism of subjects with a low insulin response was studied. During pregnancy, the insulin response of the low responders was enhanced as in the controls, but at all stages the insulin response was significantly less than in the controls. None of the subjects developed glucose intolerance during pregnancy. The fasting blood glucose and plasma insulin levels and the k-value in intravenous glucose tolerance tests (IVGTT) were modified according to similar patterns in both groups. The sensitivity to endogenous insulin was significantly greater in the low insulin responders but was reduced to a greater extent than in the controls towards the end of pregnancy. In four of the 11 low insulin responders the initial insulin response to glucose in the last trimester was lower than in mid-pregnancy. This occurred only in one out of 14 high insulin responders. It is suggested that gestational diabetes occurs in those low insulin responders who demonstrate either a dramatic decrease in insulin sensitivity, or limitations in the enhancement of insulin release, or, more likely both conditions.