Plasma glucagon levels were measured in young individuals with severe, insulin-dependent, juvenile-onset diabetes mellitus to study whether differences in glucagon secretion were related to ketosis proneness and resistance. Fasting glucagon levels were similarly elevated in both classical, ketosis-prone, type I diabetic subjects and ketosis-resistant, type “J” subjects [70 ± 7 pmol/L (mean ± SEM) and 81 ± 10 pmol/L, respectively] compared with nonobese, nondiabetic controls (36 ± 3 pmol/L, P < 0.01). After oral glucose administration, however, glucagon responses were strikingly dissimilar in the two groups. In type I diabetic individuals, glucagon rose paradoxically during OGTT, by 21 ±4 pmol/L, an increase of 33 ± 10%; on the other hand, glucagon levels in type“J”diabetic individuals fell by 28 ± 7 pmol/L, a decrease of 33 ± 5%. There was no measurable increase in plasma free insulin during OGTT in either group. Postprandial glucagon suppressibility may be relevant to the ketosis resistance that is characteristic of type “J” diabetes.

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