Metabolic research in monozygotic twins with diabetes mellitus: progress report.

An intravenous and oral glucose tolerance test and an intravenous tolbutamide test have been performed in 11 MZ twin pairs, discordant for diabetes mellitus. Blood sugar, immunoreactive insulin, and free fatty acids were determined. The research aimed at finding out whether prediabetic subjects may show any characteristic parameter which could be suggestive of the hereditary disposition. Three MZ twins of juvenile diabetics showed a normal blood glucose, immunoreactive insulin, and free fatty acids during the glucose and tolbutamide loads within a maximum of 10 years observation.