Androgens and fertility.

Androgens play a pivotal role in the development of the male reproductive tract. The spermatogenesis requires high levels of intratesticular testosterone secreted by the Leydig cells. Testosterone exerts its action through the androgen receptor (AR), which is located both in the cytoplasm and in the nucleus of cells in the target tissue. Severe defects of the AR may result in abnormal male sexual development, while more subtle modifications can be a potential cause of male infertility. Low circulating levels of testosterone can be found in 20-30% of infertile men, but administration of testosterone or gonadotropins does not result in improved sperm production. Abuse of anabolic steroids is a frequent cause of male infertility, and substances such as endocrine disruptors can alter male fertility through an anti androgenic action.