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Causes

By Mayo Clinic staff

Sperm production is complex and requires normal functioning of the testicles (testes) as well as the hypothalamus and pituitary glands — organs in your brain that produce hormones that trigger sperm production. Once sperm are produced in the testicles, delicate tubes transport them until they mix with semen and are ejaculated out of the penis. Problems with any of these systems can affect sperm production. In addition, a number of issues can cause abnormal sperm shape (morphology) or movement (motility). Often the cause of low sperm count isn't ever identified.

Medical causes
Low sperm count can be caused by a number of health issues and medical treatments. Some of these include:

  • Varicocele. A varicocele is a swelling of the veins that drain the testicle. This may prevent normal cooling of the testicle, leading to reduced sperm count and fewer moving sperm.
  • Infection. Some infections can interfere with sperm production and sperm health or can cause scarring that blocks the passage of sperm. These include some sexually transmitted diseases (STDs), including chlamydia and gonorrhea; inflammation of the prostate (prostatitis); inflamed testicles due to mumps (mumps orchitis); and other infections of the urinary tract or reproductive organs.
  • Retrograde ejaculation. This occurs when semen enters the bladder during orgasm instead of emerging out of the tip of the penis. Various health conditions can cause retrograde ejaculation, including diabetes, multiple sclerosis, spinal injuries, and surgery of the bladder, prostate or urethra. Retrograde ejaculation can also be caused by certain medications — particularly medications for enlarged prostate, such as terazosin (Hytrin), tamsulosin (Flomax) and alfuzosin (Uroxatral).
  • Lack of ejaculation. Some men with spinal cord injuries or certain diseases can't ejaculate semen, even though they still produce sperm.
  • Antibodies that attack sperm. Anti-sperm antibodies are immune system cells that mistakenly identify sperm as harmful invaders and attempt to eliminate them. This is especially common in men who've had a vasectomy.
  • Tumors. Cancers and nonmalignant tumors can affect the male reproductive organs directly, or can affect the glands that release hormones related to reproduction (such as the pituitary gland). In some cases, surgery to treat tumors can affect male fertility.
  • Undescended testicles. In some males, during fetal development one or both testicles fail to descend from the abdomen into the sac that usually contains the testicles (scrotum).
  • Hormone imbalances. Infertility can result from disorders of the testicles themselves or an abnormality affecting the glands in the brain that produce testosterone and other hormones that control the testicles (the hypothalamus or pituitary glands). Low testosterone (male hypogonadism) and other hormonal problems have a number of possible underlying causes.
  • Sperm duct defects. The tubes that carry sperm can be damaged by illness or injury. Some men are born with a blockage in the part of the testicle that stores sperm (epididymis) or a blockage of one of the tubes that carry sperm out of the testicles (vas deferens). Men with cystic fibrosis and some other inherited conditions may be born without sperm ducts altogether.
  • Chromosome defects. Inherited disorders such as Klinefelter's syndrome — in which a male is born with two X chromosomes and one Y chromosome instead of one X and one Y — cause abnormal development of the male reproductive organs.
  • Problems with sexual intercourse. These can include trouble keeping or maintaining an erection sufficient for sex (erectile dysfunction), premature ejaculation, painful intercourse, or psychological or relationship problems that interfere with sex.
  • Celiac disease. A digestive disorder caused by sensitivity to gluten, celiac disease can cause male infertility. Fertility may improve after adopting a gluten-free diet.
  • Certain medications. Testosterone replacement therapy, long-term anabolic steroid use, cancer medications (chemotherapy), certain antibiotics, some ulcer medications and certain other medications can impair sperm production and decrease male fertility.

Environmental causes
Overexposure to certain environmental elements such as heat, toxins and chemicals can reduce sperm production or sperm function. Specific causes include:

  • Pesticides. Some men exposed to pesticides such as ethylene dibromide and organophosphates have lowered sperm counts. Pesticide exposure has also been linked to testicular cancer. Most studies have been done on men who work in agriculture or live in agricultural areas.
  • Heavy metal exposure. Exposure to lead or other heavy metals also may cause infertility.
  • Exposure to radiation or X-rays. Exposure to radiation can reduce sperm production. It can take several years for sperm production to return to normal. With high doses of radiation, sperm production can be permanently reduced.
  • Overheating the testicles. Frequent use of saunas or hot tubs may temporarily lower your sperm count. Sitting for long periods or wearing tight clothing also may increase the temperature in your scrotum and reduce sperm production.
  • Prolonged bicycling. Prolonged bicycling is another possible cause of reduced fertility due to overheating the testicles. In some cases, bicycle seat pressure on the area behind the testicles (perineum) can cause numbness in the penis and erectile dysfunction.

Health, lifestyle and other causes
Some other causes of low sperm count include:

  • Illegal drug use. Anabolic steroids taken to stimulate muscle strength and growth can cause the testicles to shrink and sperm production to decrease. Use of cocaine or marijuana may temporarily reduce the number and quality of your sperm as well.
  • Alcohol abuse. Heavy drinking can lower testosterone levels, cause erectile dysfunction and decrease sperm production. Liver disease caused by excessive drinking may also cause fertility problems.
  • Tobacco smoking. Men who smoke may have a lower sperm count than do those who don't smoke. Secondhand smoke also may affect male fertility.
  • Emotional stress. Stress may interfere with certain hormones needed to produce sperm. Your sperm count may be affected if you experience severe or prolonged emotional stress. A problem with fertility itself can sometimes become long term and discouraging, producing stress.
  • Vitamin deficiency. Deficiencies in nutrients such as vitamin C, selenium, zinc and folate may contribute to decreased sperm production and male infertility.
  • Weight. Obesity can cause hormone changes that reduce male fertility. Men who are underweight also may have reduced fertility.
  • Age. Men older than 35 begin to have a gradual decline in sperm production.
  • Incomplete sperm collection. Lower than normal sperm counts can result from testing a sperm sample that was taken too soon after your last ejaculation; was taken too soon after an illness or stressful event; or didn't contain all of the semen you ejaculated because some was spilled during collection. For this reason, results are generally based on several samples taken over a period of time.
Risk factors Symptoms
References
  1. Guzick DS. Evaluation of the infertile couple. http://www.uptodate.com/home/index.html. Accessed May 7, 2010.
  2. Sigman M, et al. Male infertility. In: Wein AJ, et al. Campbell-Walsh Urology. 9th ed. Philadelphia, Pa.: Saunders; 2007. http://www.mdconsult.com/das/book/body/198188923-5/0/1445/22.html. Accessed May 7, 2010.
  3. Swerdloff  RF, et al. Evaluation of male infertility. http://www.uptodate.com/home/index.html. Accessed May 7, 2010.
  4. Bulun SE, et al. Infertility and subfertility in men. In: Kronenberg HM, et al. Williams Textbook of Endocrinology. 11th ed. Philadelphia, Pa.: Saunders; 2008. http://www.mdconsult.com/das/book/body/199429868-3/0/1555/120.html?tocnode=54107480&fromURL=120.html#4-u1.0-B978-1-4160-2911-3..50020-0--cesec90_1743. Accessed May 7, 2010.
  5. Swerdloff RF, et al. Causes of male infertility. http://www.uptodate.com/home/index.html. Accessed May 7, 2010.
  6. Leibovitch I, et al. The vicious cycling: Bicycling related urogenital disorders. European Urology. 2005;47:277.
  7. Wang C, et al. Treatment of male infertility. http://www.uptodate.com/home/index.html. Accessed May 7, 2010. Accessed May 10, 2010.
  8. Eskenazi B, et al. Antioxidant intake is associated with semen quality in healthy men. Human Reproduction. 2005;20:1006.
  9. Jurewicz J, et al. Environmental factors and semen quality. International Journal of Occupational Medicine and Environmental Health. 2009;22:305.
  10. Agarwal A, et al. Prevention of oxidative stress injury to sperm. Journal of Andrology. 26;6:2005.
  11. Agarwal A, et al. Carnitines and male infertility. Reproductive BioMedicine Online. 2004;8:376. http://www.rbmonline.com/4DCGI/Article/Detail?38%091%09=%201200%09. Accessed May 7, 2010.
  12. Burns LH. Psychiatric aspects of infertility and infertility treatments. Psychiatric Clinics of North America. 2007;30:689.
  13. Hornstein MD, et al. Optimizing natural fertility in couples planning pregnancy. http://www.uptodate.com/home/index.html. Accessed May 7, 2010.
DS01049 June 11, 2010

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