Seems to play a role in testicular function. May be a trophic hormone with a role in testicular descent in fetal life. Is a ligand for LGR8 receptor (By similarity). Heterodimer of a B chain and an A chain linked by two disulfide bonds. Expressed exclusively in Leydig cells of the testis. Male mice exhibit bilateral abdominal cryptorchidism due to alteration of gubernaculum development. Belongs to the insulin family.