In our patient, low insulin and IGF-2 levels, along with negative anti-insulin receptor autoantibodies, were documented, in contrast to patients with non-islet cell tumors, who typically exhibit elevated concentrations of IGFBP-1, IGFBP-2, and circulating free IGF-1 and IGF-2 [11-15]. This finding supports our hypothesis of excluding both insulin-mediated and paraneoplastic IGF-2-mediated glucose utilization as potential factors contributing to the low glucose levels in our patient [13]. The gene discussed is IGFBP1; the disease is pancreatic neuroendocrine tumor.