Patients with type 1 diabetes frequently develop glomerular hyperfiltration early in the course of their disorder.[9] Adequate insulin therapy does not correct this phenomenon.[10] In contrast, patients with type 2 diabetes, in whom insulin and C-peptide levels are within or above the normal range, do not show glomerular hyperfiltration or hypertrophy.[11, 12] The mechanism underlying the beneficial effect of C-peptide on renal function in diabetes is not known. This evidence concerns the gene INS and type 1 diabetes mellitus.