Although there was no convincing association between 24-hour 8-oxoGuo excretion and HbA1c, we did find higher 8-oxoGuo excretion levels with increasing insulin, c-peptide and HOMA-IR, indicating a connection between 8-oxoGuo and the hyper-insulinemic, insulin resistant state of metabolic disease, which in this morbidly obese study population was not exclusive for patients with diabetes. This evidence concerns the gene INS and metabolic disease.