A proper function of a complex system of organs and hormones is required for a male to be fertile. The critical step for reproduction is the initiation of the process in the area of the brain called the hypothalamus-pituitary axis, a system of glands, hormones, and neurotransmitters. Gonadotropin-releasing hormone (GnRH) from the hypothalamus prompts the pituitary gland to manufacture follicle-stimulating hormone (FSH) and luteinizing hormone (LH). FSH maintains sperm production, and LH stimulates the production of the male hormone testosterone.
Sperm are manufactured in microscopic tubes seminiferous tubules, which make-up most of the testicles. Surrounding these tubules are clumps of tissue containing so-called Leydig cells which surrounds the seminiferous tubules produces testosterone.
A variety of disorders ranging from hormonal disturbances to physical problems, to psychological problems can be the cause of male infertility. Male infertility caused by testicular damage is analogous to menopause for women and cannot usually be treated. Damaged testicle will fail to produce sperms. Besides testicular damage, the main causes of male infertility are low sperm production and poor sperm quality.