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Causes of Male Infertility

There are many possible causes of male infertility, and few men with fertility problems have hormonal imbalances or show any obvious signs or symptoms of their condition. We list the ten most common causes of low male fertility and why some men are less fertile than others simply because:–

  1. They don’t make enough sperm that can reach an egg and fertilise it
  2. Their sperm can’t fertilise an egg, or their DNA isn’t able to create healthy pregnancies

The standard semen sample test is the first and often the last check that men have, and it assesses sperm numbers and shapes to see if enough sperm are likely to reach an egg to fertilise it. There are also Additional sperm tests that can check whether sperm can fertilise eggs and are likely to create healthy pregnancies. These additional sperm tests are relatively new, and up to 80% of “unexplained male infertility” is due to problems with sperm that only show up with these additional tests.

It’s always disappointing for men who provide poor semen samples, but significant improvements are possible for most. Thankfully our understanding of the causes of male infertility has increased since the advent of ICSI, and we’ve learned practical ways to improve sperm quality.

10 Factors that reduce male fertility

  1. Obstructions in the testes or their tubes
  2. Raised testicular temperature
  3. Environment and lifestyle
  4. Illnesses
  5. Erectile and ejaculation problems
  6. Hormonal problems
  7. Oxidative stress
  8. “Other” factors
  9. Age
  10. Drugs

(1) Obstructions

Obstructions can prevent semen from leaving the penis in the ejaculate, and the usual causes for this are:

  1. Physical trauma to the testes and scrotum has caused bleeding and swelling
  2. Twisting (torsion) of the testes and the tubes that lead from them
  3. Inherited abnormalities of the genital ducts that obstruct or restrict the passage of semen in the tubes
  4. Abdominal surgery, which is usually for un-descended testes, hernia repair, prostate surgery, hydrocele correction, or a vasectomy
  5. After a sexually transmitted infection (usually Chlamydia or Gonorrhoea), which scar and block the tubes

(2) Raised testicular temperature

  1. Illnesses or infections (such as influenza (‘flu) and scarlet fever) that raise body temperature will reduce male fertility for up to three months. However, some viruses, especially mumps, cause orchitis (swelling of the testes), which can cause long-term male infertility
  2. Tight clothing, being obese or lifestyle choices like heated seats all raise the temperature around the testes and reduce sperm health
  3. Varicoceles also raise testicular temperature due to the extra blood circulating there

(3) Environmental and lifestyle factors

  1. Diet choices, caffeine, alcohol and cigarette smoking all increase toxins to sperm and reduce their health
  2. Pollutants in the environment, home or from occupations are toxic to sperm or alter their DNA and the child’s health
  3. Obesity or being overweight often causes metabolic syndrome, and the inflammation involved in this reduces male fertility
  4. Cycling or motorcycling restricts blood flow and raises scrotal temperatures
  5. Chemotherapy, radiotherapy treatment or ionising radiation within the last two years will affect fertility
  6. Drugs such as anabolic-androgenic steroids, marijuana, cocaine, methamphetamines, and opium-based narcotics reduce male fertility. The act by altering the hypothalamic-pituitary-testicular axis, how sperm function, and the structure of the testes i
  7. Many prescription drugs (drugs and male fertility) also affect hormones and damage sperm

(4) Illnesses that lower male fertility

  1. Diabetes reduces male fertility because of the associated damage to the automatic nervous system and blood flow
  2. Hypertension (high blood pressure) can directly cause erectile issues, and the medication that’s taken to control it often does!
  3. Coronary artery disease can cause erectile problems and hardening of the arteries in the penis (as well as the heart), plus the drugs that treat it reduce fertility
  4. Neurological disorders (including multiple sclerosis, stroke, and spinal cord injury) can cause erectile and ejaculation problems
  5. Chronic renal failure causes a build-up of waste products in the body, and this reduces sperm quality and increases the likelihood of erectile problems
  6. Cancers affecting the genital tract or endocrine (hormone) systems can directly reduce fertility, plus the drug and radiation treatments to treat any cancer can reduce or stop sperm production
  7. Stress causes changes in the body’s hormonal balance and reduces fertility; of course, fertility-related anxiety can be a significant stressor

(5) Sexual problems

Sexual problems are the main infertility issue for about 5% of couples, and we explore the physical and psychological causes in other articles.

  1. Erectile dysfunction (inability to get/maintain an erection adequate for intercourse)
  2. A lack of libido
  3. Premature ejaculation
  4. Failure to ejaculate, or “retrograde” ejaculation (where the semen goes into the bladder)
  5. The man is unable to penetrate the vagina for other reasons

(6) Hormonal problems

  1. Testosterone deficiency is a common cause of lower male fertility, and the root cause can be problems with either the testes, the pituitary gland or the hypothalamus. Testing is needed to work out which of these is the issue
  2. Hyperprolactinaemia is a condition caused by excess prolactin release from the pituitary gland. It’s usually discussed concerning female fertility as it stops menstrual cycles. However, it also can reduce male fertility and men who express milk from their nipples will have this condition
  3. A man’s body weight alters his relative hormone levels as carrying more fat increases leptin and estrogen levels while reducing his testosterone levels. Men of low body weight can also have problems due to low hormone levels, in a condition called “hypogonadotrophic hypogonadism” which means “low sex hormone levels causing sex organs to under-function.”

(7) Oxidative stress

Oxidative stress is a significant male fertility issue, and we explain why and how to reduce it in this article.

(8) Other factors

  1. Genetic problems are difficult to see, but 2-20% of infertile men have inherited factors such as Klinefelter’s syndrome
  2. Leukocytospermia (white blood cells in the semen sample) indicates infections and high oxidative stress
  3. Anti-sperm antibodies in semen samples
  4. Age as simply being an older man (over 45) can reduce fertility by up to 80%
  5. “Free radicals” and other markers of oxidative stress are higher in semen samples from infertile men, which is now considered a leading cause of male infertility
  6. Nutrition, with low concentrations of essential minerals and vitamins in the semen of infertile men

(9) Male age

Male Age is a significant fertility factor for both sexes, as this article explains.

(10) Drugs

Drugs are designed to change body function, and both legal and illegal options can dramatically reduce male fertility.

i The Insults of Illicit Drug Use on Male Fertility’. Carolyn M. Fronczak, et al. Journal of Andrology Volume 33, Issue 4, pages 515–528, July-August 2012. DOI: 10.2164/jandrol.110.011874
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