The Leydig Cell as a Target for Toxicants

Leydig cells are the testicular cells responsible for the biosynthesis and secretion of androgens, which are critical for the development of the reproductive tract and for reproductive function in the male. There are two distinct populations of Leydig cells: fetal Leydig cells (FLCs), which originate and function in the fetus but largely regress soon after birth, and adult Leydig cells (ALCs). FLCs produce high levels of testosterone (T) required for the stimulation of male sexual differentiation and testis descent. ALCs form from precursor cells during postnatal life. The adult cells produce high levels of T required for maintaining spermatogenesis and male secondary sexual characteristics in adult life. A number of environmental toxicants have been shown to disrupt FLC function, ALC development, and/or ALC function. Based on when in the life cycle cells are exposed, exposures to toxicants have been shown to have a variety of pathological consequences, including hypospadia and cryptorchidism, resulting from exposures of FLCs; delayed puberty, resulting from Leydig cell precursor cell postnatal exposures; or hypogonadism and infertility, resulting from ALC exposures.