Youth-onset type 2 diabetes has many unique features distinguishing it from adult onset and appears more severe than in adults, with youth having markedly lower insulin sensitivity (SI); fasting and stimulated insulin and C-peptide secretion that is approximately twice as high; lower stimulated glucagon and glucagon-like peptide-1 (GLP-1) secretion; less response to diabetes medications and lifestyle interventions regarding weight loss; β-cell function and glycemic control; and more rapid onset of pancreatic β-cell failure, cardiovascular, and kidney disease [4-8]. This evidence concerns the gene GCG and type 2 diabetes mellitus.