A total of twenty-five monozygotic and dizygotic glucose-tolerant twin siblings of diabetic patients were compared with age-, sex-, and weight-matched groups of glucose-tolerant offspring of two diabetic parents and normal control subjects with regard to glucose, insulin, free fatty acid and growth hormone responses during a five hour oral glucose tolerance test. Few differences in mean levels of glucose, insulin or free fatty acids were found, the trend being a higher insulin level in the twin study groups. Although the numbers of subjects were small, significantly higher insulinglucose relationships were found in monozygotic females compared to normals and in dizygotic females compared to offspring and to normals. The fasting plasma free fatty acid level was highest in the twins among each of the four subgroups, possibly indicating a blunting of the antilipolytic effect of the basal insulin level in the twins.

A “paradoxic” type of growth hormone response was seen in both the twin and offspring groups compared to the respective normal groups.

It appears that alterations in insulin-glucose relationships and growth hormone response exist in potential diabetic groups that cannot be accounted for by small but important differences in age, weight, or glucose tolerance.

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