Male infertility can be devastating for couples trying to have children and can lead to severe emotional distress. One of every five couples seeks treatment for infertility, and in up to 50% of cases, the male partner is identified to be a cause of infertility. Male infertility can occur due to many causes, including genital defects, sperm transport blockage, erection and ejaculation failure, deficient sperm production and function, surgery, and toxic or environmental exposures. Male infertility may occur when there are abnormalities in sperm identified by abnormal semen analysis testing.
Semen analysis describes sperm count, sperm concentration, sperm shape (morphology), sperm movement (motility), acidity (pH), and quantity (volume). Normal reference values are defined by the World Health Organization (WHO) criteria and include total sperm count of 39 million sperm per ejaculate, sperm concentration of 15 million/ml, 40% total motility, 4% morphologically normal, 1.5 ml volume. Infertiility may occur may occur above these values or when there is decreased sperm number (oligospermia, <20 million sperm per milliliter), decreased quality of sperm (abnormal shape, movement, sperm DNA), or complete absence of sperm (azoospermia).
Oligospermia (low sperm count) can have many causes, often unknown, and is usually identified along with abnormalities in the sperm (movement, shape, or DNA issues). Azoospermia (no sperm in the ejaculate) is identified in 15% of infertile men. There are two general categories which explain the cause of having decreased or no sperm in the ejaculate: obstructive azoospermia (OA, 40% of all cases of azoospermia) and non-obstructive azoospermia (NOA) which includes the rest of men with azoospermia. These are exactly what they sound like: obstructive azoospermia (OA) results from a blockage along the genital tract somewhere between the testicle (where sperm are produced) and the ejaculatory duct (where the semen enters the urethra during ejaculation) to leave the body. Other parts of the genital tract can also be blocked (the technical names include the rete testis, efferent ducts, epididymis (sperm maturation takes place here), vas deferens, and ejaculatory duct). Non-obstructive azoospermia (NOA) involves impairment or absence of sperm production (spermatogenesis) due to a variety of causes. For more detail see our posts on specifics of OA and NOA.