Decreased half-life of insulin-like growth factor I in Rabson-Mendenhall syndrome

Rabson-Mendenhall syndrome is an autosomal recessive disorder of insulin si gnalling caused by mutations in the insulin receptor gene. Affected patient s are insensitive to exogenous insulin. Insulin-like growth factor I (IGF-I ), whose receptor is similar to the one for insulin and is not impaired in this condition, is not always effective in these patients. To understand th e reason for this failure, IGF-I concentrations were measured in a patient after subcutaneous injection of 0.1 and 0.2 mg/kg or rhIGF-I. IGF-I concent rations increased only transiently because or the short half-life (1.3 -3 h . compared to a normal range of 17-22 h). No correlation was found between IGF-I concentrations and glucose or insulin concentrations. The short half- life or IGF-I may contribute to treatment failure in patients with inherite d insulin-resistant syndromes.