IGF1 and hyperinsulinemic hypoglycemia, familial, 4: The mechanisms mainly involved are synthesis of insulin-like growth factors; isolated IGF deficiency (IGF1, IGF2), transport/bioavailability of IGFs; ternary complex defect (due to mutations in IGFALS, PAPPA2 and STC2); and IGF-1 sensitivity (due to mutations in IGF1R).