Insulin is a pancreatic hormone that regulates glucose and is involved in the synthesis of proteins and fat. Insulin increases cell permeability to monosaccharides, amino acids, and fatty acids. It accelerates glycolysis, the pentose phosphate cycle, and glycogen synthesis in liver. Insulin is a heterodimer of a B chain and A chain linked by two disulfide bonds. Defects in Insulin are the cause of familial hyperproinsulinemia. Insulin is available under brand names Humulin or Humalog (Eli Lilly) and Novolin (Novo Nordisk) when used for the treatment of diabetes.