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What are the main causes of infertility in men?

This section covers the most common causes of infertility in men.


Azoospermia is a male condition in which no sperm is being produced or the sperm are not evident in the semen. The condition can be a result of a hormonal imbalance or physical blockage. Medical intervention may be required to bring hormones back in balance or to clear the blockage.

Below are descriptions of the two 2 main types of azoospermia.

Obstructive Azoospermia (sperm transport problems)

Of all cases of azoospermia, obstructive azoospermia accounts for 40%. For sperm to leave the body, it must travel from the testes to the urethra. Sperm cells pass through a series of ducts in the reproductive system before they mix with the ejaculate and exit the body. At times, blockages can form inside these ducts that prevent sperm from mixing with the ejaculate. These sperm transport problems can be caused by:

  • Absence of the vans deferens (congenital): The vas deferens is a tiny tubal structure that carries sperm to the urethra for ejaculation. There are some men who are born without the vas deferens.
  • Torsion: Torsion, a relatively common condition, is caused by an abnormality in the supportive tissue that allows the testes to twist inside the scrotum. Characterized by extreme swelling, torsion pinches the blood vessels that feed the testes shut. The result is testicular damage. If urgent surgery is not conducted to untwist the testes, torsion can cause serious impairment to fertility and cause permanent infertility if both testes twist and are not corrected immediately. 
  • Vasectomy: A vasectomy cuts the connection or creates a blockage to the vas deferens, which prevents sperm from mixing with the ejaculate.
  • Retrograde Ejaculation: Retrograde ejaculation occurs when the semen is ejaculated into the bladder instead of through the urethra. This is because the bladder sphincter muscle does not close properly during ejaculation. With this disorder, ejaculate volume is small, and after ejaculation, urine may be cloudy. Retrograde ejaculation is the cause of infertility in 1.5% of infertile men. It can often be controlled by medications such as decongestants that contract the bladder sphincter muscle. Normal ejaculation can also be restored through surgical reconstruction of the bladder neck.
  • Infection: There are some infections that can create blockages in the epididymis or vas deferens, which prevents the sperm from combining with the semen.

Non-obstructive azoospermia (sperm production problem)


Non-obstructive azoospermia is the lack of sperm production by the testicles. The condition is often the result of hormonal imbalances. At times, the body may under-produce certain sperm-making hormones involved in the process, which can cause azoospermia.

Below are several of the main root causes of non-obstructive azoospermia:

Cryptorchidism: Cryptorchidism, or undescended testicles, is a genital condition in which the testes have not properly descended. The condition is typically corrected in childhood. However, if not corrected, the testicles will not be able to properly produce sperm.

  • Klinefelter’s Syndrome: With this genetic condition, each cell in the body has an additional X chromosome, meaning that males with Klinefelter’s Syndrome have one Y and two X chromosomes. The physical symptoms of this condition include both small testicles and enlarged breasts. To confirm this condition, a chromosome analysis is performed. When treated in its early stages (the drug hCG is used), the man's body may start to produce sperm or improve production. Eventually, Klinefelter’s Syndrome causes atrophy in all active testicular structures. It is important to note that once testicular failure has occurred, it is impossible to improve fertility.
  • Orchitis: Orchitis is the inflammation and swelling of one or both of the testicles. The condition is usually caused by a bacterial or viral infection. There are different treatments for orchitis, depending on the cause and state of advancement. The symptoms of viral infections are treated with anti-inflammatories; bacterial infections are typically treated with antibiotics.
  • Vascular Trauma: Trauma to the testes or the blood vessels within the testes can hinder sperm production.
  • Varicoceles: An enlargement of the internal spermatic veins (that feed blood from the testicle to the abdomen and back to the heart) is called a varicocele. These enlarged veins cause blood to pool in the testes, which impairs the production of sperm. A varicocele may cause elevated scrotal temperature, pain and/or impaired semen quality. In addition, it may reduce sperm count and cause abnormal sperm morphology, which can result in infertility. Physicians can typically diagnose varicoceles with a physical examination of the scrotum, aided by a scrotal ultrasound and Doppler stethoscope. The most successful varicocele treatment is corrective surgery, but other alternatives are available. 
  • Radiotherapy: Treatment using radiotherapy in the pelvic area for cancer and other conditions can cause non-obstructive azoospermia.

Over half of non-obstructive azoospermia cases do not have definite identified causes (idiopathic).



Oligospermia, or low sperm count, is generally defined as fewer than 20 million spermatozoa per milliliter of ejaculate. The condition can be the result of a variety of factors, some of which are reversible and some of which are permanent. A common cause of oligospermia is an obstruction in normal sperm flow due to testicular trauma, vasectomy or scarring from reproductive-system surgery, infection or sexually transmitted diseases.

Oligospermia can also be caused by a decrease in sperm production due to hormonal disorders, varicoceles, testicular diseases or obesity. Other oligospermia causes include smoking, stress, drug or alcohol use, specific medications, toxin exposure, malnutrition or being underweight. Oligospermia can also result from some sexually transmitted diseases, such as gonorrhea or chlamydia.


Teratozoospermia is the occurrence of sperm cells with abnormal or unusual structure that causes infertility in men. Teratozoospermia typically decreases sperm motility and prevents the sperm cells from breaking through the ovum membrane for fertilization.




In necrospermia, the spermatozoa in seminal fluid are dead or not moving. Bacterial infection is one cause of necrospermia.


Anti-inflammatories or diuretics can treat necrospermia when caused by prostatitis, seminal vesiculitis, orchitis or epididymitis.


Asthenozoospermia is defined as reduced sperm motility. In the ejaculate, when the count of actively swimming sperm is very low, or if sperm movement is impaired, there are reduced chances of a sperm reaching and fertilizing the egg following intercourse.

Other infertility factors

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