In addition to the effects of exendin-(9-39) on baseline islet cAMP and insulin secretion, exendin-(9-39) inhibited amino acid-stimulated insulin secretion, a key phenotypic feature of hyperinsulinism due to inactivating mutations in the KATP channels where consumption of protein leads to insulin secretion and hypoglycemia (30, 31). This evidence concerns the gene INS and hyperinsulinism.