Elder DA, et al. - An exploration was pursued of the proposition that at the time of diagnosis with type 2 diabetes mellitus (T2DM), adolescents would have impaired β-cell function illustrated via the disposition index (calculated as: Insulin secretion adjusted for insulin sensitivity). This would be followed by a rapid decline of function irrespective of the standard medical management. The β-cell function exhibited an impairment with no improvement of β-cell function over the 2 years of study regardless of the stable Hemoglobin A_1c, body mass index markers of insulin sensitivity, and standard treatment of hyperglycemia.