Too Much Glucagon, Too Little Insulin: Time course of pancreatic islet dysfunction in new-onset type 1 diabetes

OBJECTIVE—To determine the time course of changes in glucagon and insulin secretion in children with recently diagnosed type 1 diabetes. RESEARCH DESIGN AND METHODS—Glucagon and C-peptide concentrations were determined in response to standard mixed meals in 23 patients with type 1 diabetes aged 9.4 ± 4.6 years, beginning within 6 weeks of diagnosis, and every 3 months thereafter for 1 year. RESULTS—Glucagon secretion in response to a physiologic stimulus (mixed meal) increased by 37% over 12 months, while C-peptide secretion declined by 45%. Fasting glucagon concentrations remained within the normal (nondiabetic) reference range. CONCLUSIONS—Postprandial hyperglucagonemia worsens significantly during the first year after diagnosis of type 1 diabetes and may represent a distinct therapeutic target. Fasting glucagon values may underestimate the severity of hyperglucagonemia. The opposing directions of abnormal glucagon and C-peptide secretion over time support the link between dysregulated glucagon secretion and declining β-cell function.