Exogenous administration of testosterone synthesis derivatives induces negative feedback on the hypothalamic-pituitary axis and therefore inhibiting the secretion of both FSH and LH. Thus, if there is decreased production of FSH/LH, the testes do not perform their normal fertility function with the production of sperm in men alongside their role in producing the sex hormones.
Infertility after AAS abuse commonly presents as oligozoospermia (low sperm concentration) or azoospermia (absence of sperm in ejaculate), associated with abnormalities in sperm motility and morphology.
Depending upon the sperm count, the chance of conception can be lower than at a healthy man. The smaller sperm count is, the chance to conceive decreases. However, chances are very good if a female partner is fertile.
Erectile dysfunction and libido loss may also occur, especially after discontinuation, when endogenous testosterone levels are usually low.