When this condition is investigated the blood insulin levels fail to fall even under quite severe hypoglycaemia. Normally endogenous insulin has a half life of about four minutes, and thus responds rapidly to hypoglycaemia.
One of the important differentials is exogenous administration of insulin - for example by a parent with Munchausen's syndrome by proxy. However, measurement of C-peptide levels in the urine will be raised in nesidioblastosis - they are not seen in exogenously administered insulin.
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