The influence of a glucose load on subsequent carbohydrate metabolism in pregnancy

Two separate independent exercises comparing 50 g with 75 g and 100 g oral glucose tolerance tests (OGTT) were performed in Chinese pregnant women. We found a significant difference in fasting values between the paired OGTTs when the 100 g test preceded the 50 g test. The fasting glucose levels on the second occasion of testing were significantly lower than on the first testing. The difference was less pronounced when the first glucose load was 75 g and was insignificant when the 50 g test was given first. The blood glucose response to glucose loads was also significantly altered on the second occasion of testing, again in proportion to the size of the first glucose load. We postulate that this influence of glucose tolerance testing on subsequent carbohydrate metabolism results either from sensitization of the pancreatic islet cells or from sensitization of tissues, resulting in increased rate of glucose utilization. We also suggest that an 1,800 Kcal diet represents an increase in carbohydrate load over their normal diet for many of our patients. In patients with mildly deranged OGTT, improvement in the glucose profile on diet may be due to this phenomenon rather than to a decrease in carbohydrate as is believed.