What is azoospermia?

Azoospermia is a lack of sperm in seminal fluid. If, after one year of unprotected sex, a pregnancy has not occurred, this means that the man, woman, or both, may have a fertility problem. In 40% of infertile couples, the male has a fertility problem.

How common is azoospermia?

About 1% of all men and 10%-15% of infertile men have azoospermia.

What are the types of azoospermia?

The male reproductive system is made up of the following:

  • Testes, or testicles – produce sperm (male reproductive cells) in a process called spermatogenesis
  • Seminiferous tubules – tiny tubes that make up most of the tissue of the testes
  • Epididymis – tube into which mature sperm are moved and stored
  • Vas deferens – tube that passes from the epididymis into the body cavity, then curves to connect with the urethra. Tightening of the vas deferens moves the sperm along, past the seminal vesicles and prostate gland, which add seminal fluid to the sperm to form semen.
  • Urethra - tube that runs through the penis to eliminate urine from the bladder and semen from the vas deferens

Azoospermia can be grouped into three major types:

1) Pre-testicular causes (non-obstructive): Poor production of sex hormones prevents the testicle from making sperm. Can be caused by:

  • Kallmann syndrome: A genetic (inherited) disorder carried on the X chromosome, marked by low levels of gonadotropin-releasing hormone (GnRH) and a loss of smell. GnRH stimulates the pituitary gland to secrete hormones that govern the reproductive organs.
  • Disorders of the hypothalamus (a part of the brain) or pituitary gland, which can be caused by radiation treatments or certain medications, especially those used in chemotherapy.

2) Testicular causes (non-obstructive): defects in the structure or functioning of the testicles. Can be caused by:

  • Anorchia (absence of the testicles)
  • Cyptorchidism (testicles have not dropped into the scrotum)
  • Sertoli cell-only syndrome (testicles fail to produce living sperm cells)
  • Spermatogenic arrest (testicles fail to produce fully mature sperm cells)
  • Klinefelter’s Syndrome; male carries an extra X chromosome (making his chromosomal makeup XXY instead of XY). The result is often infertility, along with lack of sexual or physical maturity, and learning difficulties.
  • Mumps orchitis (inflamed testicles caused by mumps in late puberty)
  • Tumors
  • Reactions to certain medications
  • Radiation treatments
  • Diseases such as diabetes, cirrhosis, or kidney failure
  • Surgery
  • Varicocele (veins coming from the testicle are dilated, or widened)

3) Post-testicular causes (obstructive): Problems with ejaculation or an obstruction in the reproductive tract prevents sperm from being carried into the seminal fluid. This condition occurs in about 40% of men with azoospermia. Can be caused by:

  • An obstruction or missing connection in the epididymis, vas deferens, or elsewhere in the reproductive system
  • Congenital bilateral absence of the vas deferens (CBAVD): A genetic defect in which the vasa deferentia are absent at birth. The genetic mutation that causes CBAVD is also strongly associated with cystic fibrosis. Men with CBAVD have a high risk of being a carrier of cystic fibrosis. Female partners of men with CBAVD should have a gene mutation analysis to see if they are also a carrier in order to determine the risk of having a child with cystic fibrosis.
  • Infection
  • Growth of a cyst
  • Injury
  • Vasectomy (removal of all or part of the vas deferens with surgery)

What are the causes of azoospermia?

Genetics (inheritance) plays a role in 10%-15% of men with low or no sperm production. Defects in chromosomes (the structure inside a cell nucleus that contains genetic material) can affect the number, form, and size of sperm.

Defects can occur at different locations on the Y (male) chromosome. In some cases, a piece of the Y chromosome may be missing (microdeletion) and cause infertility.