[Leydig cell development].

This review is about the study of the testis Leydig cells formation and development in prenatal and postnatal periods. Leydig cells of testis are the main place of synthesis and secretion of androgens including testosterone--the main male sexual hormone. Testosterone plays an important role in male reproduction regulation. There are two types (two populations) of Leydig cells during ontogenesis. The first type is fetal Leydig cells, which appear and function in the prenatal masculinization period of the male urogenital system. Another type is adult Leydig cells, which originate during sexual maturation postnatally. Fetal and adult Leydig cells pass the same stages both in the prenatal and postnatal periods. They are Leydig cell progenitors, immature Leydig cells and adult Leydig cells.