IGFBP1 and Hypoglycemia: In difficult to diagnose cases, supportive evidence can be provided by decreased serum levels of insulin-like growth factor-binding protein 1 (IGFBP-1) (as insulin suppresses the transcription of IGFBP-1 gene), a positive glycemic response to intramuscular/ intravenous glucagon at the time of hypoglycaemia (a clear increment in blood glucose of >1.5 mmol/L despite severe hypoglycaemia), and a positive glycemic response to octreotide (30,31).