Hypoglycaemia from any cause whatsoever (except endogenous hyperinsulinism) inhibits endogenous insulin and C-peptide secretion. This leads to a fall in peripheral venous plasma concentrations of insulin and C-peptide, to below 30pmol/l (5mu/l) and 300pmol/l (1ng/ml or 1┬╡g/l), respectively. Values greater than these in the presence of proven hypoglycaemia indicate ΓÇÿinappropriateΓÇÖ insulin secretion. Patients who suffer from insulinoma demonstrate ΓÇÿinappropriateΓÇÖ hyperinsulinaemia on some, but not necessarily all, occasions (Fig. 20.12).
