IGF-1 is a protein that in humans is encoded by the IGF1 gene. IGF-1 consists of 70 amino acids in a single
chain with three intramolecular disulfide bridges. IGF-1 has a molecular weight of 7,649 Daltons. IGF-1 is
produced primarily by the liver. Production is stimulated by growth hormone (GH). Most of IGF-1 is bound to
one of 6 binding proteins (IGF-BP). IGFBP-1 is regulated by insulin. IGF-1 is produced throughout life;
the highest rates of IGF-1 production occur during the pubertal growth spurt. The lowest levels occur in
infancy and old age.[medical citation needed] Protein intake increases IGF-1 levels in humans under age 65,
independent of total calorie consumption. A synthetic analog of IGF-1, mecasermin, is used in children for
the treatment of growth failure.