Male infertility can be caused by health issues or medical treatments which include:

Sperm Disorders

The number one cause of infertility in men, these disorders include: low sperm count (too few or no sperm in the semen), low sperm motility (sperm don’t move as well as they should), malformation of the sperm, and blocked sperm ducts (or varicocele).

Varicocele

A condition in which veins around the vas deferens (the ducts that carry sperm from the testicle to the urethra) are too large, accounting for about 30 percent of male infertility cases. In this situation, blood pools around the testicles, and the temperature inside the scrotum increases. When testicles have been too hot for too long, sperm production can be affected.

Infections

Infections can interfere with sperm production and sperm health, as well as the movement of sperm, potentially causing scarring that blocks the passage of sperm. Infection causes include:

  • sexually transmitted diseases or infections
  • prostatitis, or inflamed prostate
  • mumps orchitis, or inflamed testicles that are the result of a mumps infection
  • urinary tract or reproductive system infection

Over-the-Counter Medicines

These medications, including antibiotics, can decrease sperm count. Chemotherapy and radiation from cancer treatment can impair sperm production and decrease fertility, as can testosterone replacement therapy or long-term anabolic steroid use.

Previous Injuries

Past injuries can cause scarring in the pathways (sperm ducts) that take sperm from the testicles to the tip of the penis. Any interruption along the way can block the sperm.

Retrograde Ejaculation

A condition in which a man’s semen enters the bladder during orgasm, instead of exiting the tip of the penis, this condition makes conceiving difficult. Retrograde ejaculation can be caused by a number of conditions, including:

  • previous surgeries
  • diabetes
  • spinal injuries
  • certain medications, particularly those prescribed for enlarged prostate

Undescended Testicles

This condition, the result of one or both testicles failing to descend from the abdomen during fetal development, can interfere with sperm production and movement.

Hormone Imbalances

Hormonal imbalances can be the result of abnormally functioning glands in the brain (the hypothalamus or pituitary glands control the testicles), or disorders of the testicles. Hormonal imbalances may keep the body from signaling the release of sperm and prevent a man from having a fully functioning sex drive.

Sexual Intercourse Problems

Additional conditions which may create infertility in a couple include:

  • erectile dysfunction
  • premature ejaculation
  • painful intercourse
  • emotional or psychological problems that interfere with sex,

Environmental & Lifestyle Causes

Infertility in men may also have environmental or lifestyle causes, including:

  • Heavy metal exposure.
  • Exposure to pesticides.
  • Overheating of the testicles: Frequent use of hot tubs or saunas can temporarily affect sperm count. Laptops may also be a low-sperm culprit, too—laptops warm up the lap and scrotum of men, and prolonged use of laptops may be detrimental to fertility.
  • Tobacco, drug, and alcohol use: Men who smoke have a lower sperm count than men who don’t. The same is true for men who use cocaine or marijuana. Using anabolic steroids may also cause the testicles to shrink, reducing sperm production. Heavy or frequent drinking can cause erectile dysfunction and a decrease in sperm production.
  • Obesity: Being overweight can affect hormones that control fertility. Men who are underweight may also have decreased fertility as a result of their weight.