Insulin effect on serum potassium and autoinhibition of insulin secretion is intact in a patient with leprechaunism despite severe impairment of substrates metabolism.

Background. The effect of insulin on glucose, protein metabolism, circulating fatty acids (FFA), potassium (K+) and C-peptide concentrations were investigated in a 12-year-old girl with leprechaunism. The mutations do not affect the insulin-receptor binding affinity and insulin-stimulated auto-phosphorylation of the receptor. Methods. The subject was studied with a primed-continuous infusion of [6,6−2H2] glucose and [1-13C] leucine during a basal period followed by two steps of insulin infusion (1 and 10 mU/kg/min) of 2 h each, during which plasma glucose level decreased from 131 to 115 and then to 95 mg/dL. Conclusions. The dissociation of control exerted by insulin on K+ uptake and on β-cell secretion may rely on a differential expression and folding of the mutated receptors in the different insulin target tissues.