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To the Editor:

We thank Regelmann et al for sharing our interest in this subject and posing important clinical research questions related to medication-induced diabetes mellitus. We acknowledge the heterogeneity of our study population, but point out that our central question was whether there is a new profile of children with medication-induced diabetes in the setting of increased prevalence of overweight and obesity in children in the general population. In this group of 58 children, we did not request the primary disease, but we noted that 98% were receiving at least one diabetogenic drug and 95% were receiving a glucocorticoid. Our hypothesis was that obesity has increased the risk of β-cell exhaustion in these children, leading to a change in the age and ethnicity of affected children. We did not collect C-peptide or insulin levels, because the study was designed as a prospective national incidence surveillance study for non–type 1 diabetes mellitus.

We agree with Regelmann et al that attributable risk due to obesity can be defined by matching individuals with medication-induced diabetes to a control group with the same disease and of the same age and stage of puberty. However, the usefulness of insulin or C-peptide level remains to be determined, given that a low insulin or C-peptide level due to insulin deficiency may occur in an obese child with β-cell exhaustion or drug-induced β-cell toxicity. An elevated insulin or C-peptide level may indicate insulin resistance in a lean child receiving high-dose glucocorticoid therapy, but might not be as easy to interpret in an obese child with the same condition and treatment. Furthermore, a decreased insulin or C-peptide level in a lean or obese child with the same underlying condition and treatment regimen indicates β-cell failure, but differentiating between β-cell exhaustion and drug toxicity might be difficult.