IHH, encoded by the IHH gene in humans, belongs to the mammalian hedgehog family. It is expressed in adult kidney and liver. The function of IHH is involved in chondrocyte differentiation, proliferation and maturation especially during endochondral ossification. It regulates its effects by feedback control of parathyroid hormone-related peptide (PTHrP). IHH is also involved in yolk sac vasculogenesis, playing an important role in differentiation of epiblast cells into endothelial and red blood cells. Human IHH shares 100 % amino acid sequence identity with murine.