Causes of male infertility and fertility tests

male infertility

Male infertility is a disease defined as the inability for a man to get a fertile woman pregnant after 12 months of unprotected and timed sexual intercourse.

Male infertility is responsible for about one third of all fertility issues in a couple. Another third is due to female infertility and the remaining third is caused by a combination of the two or it is due to unknown causes. Infertility affects millions of men in the world; it is estimated that 8-12% of couples worldwide are affected by infertility and in developing countries this number could be as high as 50%.

Primary infertility and secondary infertility

The difference between primary and secondary infertility is that in primary infertility the couple has never been able to conceive a child or to deliver a live child, while in secondary infertility the couple has been previously able to give birth but can’t conceive anymore.

Although they are classified distinctly, the causes of both primary and secondary infertility are the same.

Factors affecting fertility in men

Several factors affect male fertility some of which can be corrected to increase the chances of a successful pregnancy.

  1. Age
  2. Body weight
  3. Diet
  4. Tobacco smoking
  5. Alcohol use
  6. Drugs
  7. Environmental, workplace or home exposures
  8. Stress, anxiety and depression
  9. Sexually transmitted infections (STDs)
  10. Excessive exercising
  11. Heat


Age is not a significant factor in male infertility. Although age represents one of the most important factors in female infertility and although also in men advancing age leads to changes in hormone levels and in sperm quality and quantity, all of these changes are generally subtle and in some cases insignificant with the oldest father ever being a 94 year old and many men becoming fathers after 60.

Body weight

Both being overweight and being underweight impacts male fertility with changes in hormone levels and sperm quality and quantity. Males should aim for a BMI between 20 and 25 for optimal fertility and best chances of conceiving.


The diet is important for overall health and for maintaining a healthy weight; a healthy diet is associated with higher fertility when compared to unhealthy diets. Nutritional deficiencies can affect sperm parameters; moreover, diet impacts the health of the next generation, with children born to fathers with nutritional imbalances showing a wide range of health issues.

Some evidence suggests the supplementation with antioxidants and omega-3 fatty acids may be beneficial to improve fertility in males.

Tobacco smoking

Smoking is linked to a variety of reproductive and fertility issues in men. From erectile dysfunction, to damage to DNA in sperm which can lead to health issues in the children such as an increased risk of leukemia. Smoking also affects sperm quantity, concentration, motility and shape. Since it takes about three months for sperm to mature, men should quit smoking at least three months before trying to conceive; as soon as a man quits smoking his sperm quality will quickly return to normal.

Alcohol use

Alcohol can profoundly affect both male sexual function and hormone levels. Moreover, it can have an impact on sperm maturation which leads to poor sperm quality. For optimal fertility men should avoid drinking alcohol.


Use and abuse of drugs such as marijuana and cocaine can negatively impact male fertility. From changes in sperm count, concentration, motility and morphology to reduced libido and sexual function to effects on the production and release of hormones.

Environmental, workplace or home exposures

Exposure to certain substances can play a factor or be the direct cause of male infertility. Heavy metals, pesticides, solvents, radiation and many other chemicals can influence men fertility. Check the Material Safety Data Sheets available online or at your workplace for more information on specific substances.

Stress, anxiety and depression

Stress, anxiety and depression are linked to male fertility issues. It is hard to investigate the extent of the effects, nevertheless they should be considered as a factor to address in male infertility cases.

Sexually transmitted infections (STDs)

Chronic infections such as gonorrhea can cause urethral strictures and infection of the testis with impairment of fertility. Gonorrhea and chlamydia can be transmitted to the female partner and cause pelvic inflammatory disease (PID) which can cause female infertility. These and other sexually transmitted infections may cause male infertility, but more research and evidence are needed on the subject to establish the association.

Excessive exercising

Excessive exercising can affect the amount of androgen hormones produces and released by the body. An excess of such hormones can affect and decrease fertility.


Heat affects male fertility. Spermatogenesis is temperature dependent and normal spermatogenesis occurs when the scrotal temperature is about 2-2,5 °C lower than the 37 °C core temperature. An increased temperature in the testicles or scrotal area has an effect on sperm quality and quantity. Heat exposure can be due to occupational factors, long warm baths, tight clothing, laptops, and many other sources. The effects of heat exposure may last a full sperm development cycle, about 3 months, before the sperm parameters normalize.

Causes of male infertility

Conceiving is a complex process and for men many things can go wrong along the way. Male infertility can be caused by:

  1. Testicular issues which affect formation and maturation of healthy sperm.
  2. Obstructive issues which affect the tubules that transport sperm from within the testicles to outside the body.
  3. Sexual issues which affect sexual intercourse and the ability to deliver semen into the vagina.
  4. Other issues

Testicular issues causing male infertility

Testicular issues leading to male infertility can be caused by one or more of the many factors discussed above, like smoking, bodyweight, STDs and exposure to heat or chemicals.

Varicoceles are enlarged veins in the scrotum which disrupt normal blood flow. Varicoceles are found in about 15% of males and in some of them they can be a cause of infertility. The mechanism for which varicoceles cause infertility, with changes in quantity and quality of sperm, is still not clear: it could be because of the increased scrotal temperature due to the abnormal blood flow, or because of the reduced blood perfusion of the testis, or because of some other reason.

Injury from surgery or trauma, infections and chemotherapy can also damage the testicles and cause issues with sperm production which lead to infertility.

Obstructive issues causing male infertility

Sperm are produced in the testicles and mature in small tubes called epididymis; then they flow into other tubes known as vas deferens. From there they go into the ejaculatory duct and finally into the urethra. A blockage or absence of any of such tubes, due to congenital causes, trauma, infection or a vasectomy, is a possible cause of infertility in men.

Sexual Issues causing male infertility

Sexual dysfunctions which affect male fertility can have many causes such as medications use, psychological issues such as stress, anxiety and depression, or the presence of other medical conditions.

Erectile dysfunction is the inability to get or keep an erection functional enough for having sex.

Premature ejaculation is characterized by the inability to delay ejaculation and by ejaculating within one minute of vaginal penetration. In some cases, ejaculation occurs during foreplay, before penetration or as soon as the penis touches the vagina; in such cases it can cause fertility issues.

Anejaculation is the inability to ejaculate. This can be due to the use of medications or drugs, due to psychological issues, or due to underlying medical conditions.

Retrograde ejaculation is a condition when sperm does not come out of the urethra, but instead travels back into the bladder. Man affected with this condition experience an orgasm without visible ejaculation. This condition may be caused by traumas, surgeries or certain medications such as tamsulosin.

Other issues causing male infertility

In some cases, the male partner and/or the female partner may produce anti-sperm antibodies (ASA) which are proteins produced by the immune system that target and attack the sperm inhibiting its ability to fertilize the egg.

Hormonal imbalances are another possible cause of infertility: hypothalamus, pituitary gland, thyroid, adrenal glands and the testicles themselves all produce hormones that can influence healthy sperm production.

A number of genetic issues can also cause male infertility.

Klinefelter syndrome (KS or 47 XXY) is a chromosomal abnormality causing testicular dysfunction and affecting fertility in males. It is not rarely an asymptomatic condition with no evident effects, as such many males with Klinefelter syndrome may be undiagnosed.

Y chromosome microdeletions is a chromosome abnormality where some genetic information is missing from Y chromosome which is the one containing genes that regulate sperm production.

Cystic fibrosis, Down syndrome or other DNA mutations can also be other genetic causes responsible for male infertility.

Several medications can cause infertility by interfering with sperm production or by causing a sexual dysfunction. Testosterone, chemotherapy, antidepressants, some antibiotics and other commonly prescribed medications can have an effect on male fertility.

Retrograde ejaculation which occurs when semen flows backwards into the bladder during ejaculation is another possible cause of male infertility. In this case men experience an orgasm, but there is no apparent semen release.

Male Fertility tests: diagnosing infertility in men

To assess the cause of infertility in males the first step is the medical consult by an andrologist or urologist. The physician will first take the medical and family history, ask about reproductive history, symptoms, medication use, lifestyle, possible exposures, …

After collecting all relevant information, the physician will perform a physical examination of the genitalia with palpation of the testicles.

Further steps for diagnosing infertility in men include:

  • Blood tests, to check for hormonal imbalances, nutritional deficiencies, genetic conditions or underlying pathologies.
  • Semen analysis. A semen specimen is analyzed to provide information such as semen volume, sperm concentration, motility and morphology. Signs of infection or biochemical imbalances in semen can also be detected.
  • Ultrasound. Scrotal ultrasonography and transrectal ultrasonography can detect varicoceles or obstructive causes of male infertility.

In some cases, a testicular biopsy or an MRI might be prescribed too.

Treatment options for male infertility

Treatments depend on the cause of infertility and several treatment options are available to address the different causes:

  • Lifestyle interventions. Smoking cessation, weight control, …
  • Supplements. To correct micronutrient deficiencies.
  • Medications. For other pathologies that can cause infertility including infections.
  • Counseling or medication for sexual dysfunctions.
  • Hormonal Therapy. To address hormonal imbalances.
  • Surgery. To address varicoceles, reverse a vasectomy or correct a blockage.

When the above are not indicated or are not able to solve the fertility issue in the male, there are still other options available to conceive and known as Assisted Reproductive Technologies (ART):

  1. Intra-uterine insemination (IUI) also known as artificial insemination.
  2. Intra-cytoplasmic sperm injection (ICSI)
  3. In-vitro fertilization (IVF)
  4. Percutaneous Epididymal Sperm Aspiration (PESA)
  5. Testicular sperm aspiration (TESA)

We will talk more in detail about all treatment options for male infertility in a dedicated article.

For the causes, factors, diagnosis of infertility in women, check the dedicated article on female infertility.

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    SR Bayer, MM Alper, AS Penzias – CRC Press, 2018
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    J Wall, CN Jayasena – The British Medical Journal, Oct 2018
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  • The effect of paternal age on assisted reproduction outcome.
    L Dain, R Auslander, M Dirnfeld – Fertility and Sterility, Jan 2011
  • Impact of obesity on male fertility, sperm function and molecular composition.
    NO Palmer, HW Bakos, T Fullston – Spermatogenesis, Oct 2012
  • Sexually transmitted infections: impact on male fertility.
    FR Ochsendorf – Andrologia, Apr 2008
  • Sexual dysfunction and male infertility.
    F Lotti, M Maggi – Nature Reviews Urology, Mar 2018
  • National Institutes of Health (NIH) – US Department of Health & Human Services
  • American Society for Reproductive Medicine


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