Oral Contraceptive Use and Other Factors in the Standard Glucose Tolerance Test

Abstract

Three-hour standard glucose tolerance tests were performed on 2,248 women subjects with a family history of diabetes. Use of oral contraceptives (OCs) was associated with equal elevations in one- and two-hour values but, surprisingly, lowered fasting blood sugars. A similar but weaker trend was present for other estrogen use. Increasing age correlated with higher blood glucose values at all time points of the test, most markedly at one hour. Increasing relative weight was also associated with increased values at all hours of the test; here the increase was most marked (and approximately equal) at one and two hours. The rise in glucose, however, remained relatively well sustained at three hours, in contrast to most other variables. Glycosuria in overweight women was accompanied by a greater degree of hyperglycemia than in lean subjects. A history of first-degree diabetic relatives tended to be associated with elevated values at all time points, but only at the fasting and one-hour points were the values significantly higher than those of women with lesser degrees of diabetic relationship. History of cholecystectomy was also associated with elevated glucose levels. Heavy drinkers had a high one-hour mean, with normal to low two- and three-hour tests; smoking was not associated with any differences at the fasting or one-hour points, but smokers showed significantly decreased levels at two and three hours. Principal-components analysis showed that fasting level, the “area under the curve,” and the steepness of descent from the one-hour level were completely independent aspects of the glucose tolerance test curve and could be used to summarize the original four data points of the test.