Written by Dr. Phoebe Howells. Reviewed by Jenny Wordsworth.

Dr. Phoebe has been a doctor since 2012 with a decade of experience in Obstetrics and Gynaecology focusing on fertility. She's undertaken a clinical fellowship in Reproductive Medicine at a top London fertility clinic alongside authoring articles, sharing insights at global conferences, contributing to fertility trials for women with adenomyosis and working as the Co-Chief Medical Officer for OVUM.

Infertility affects approximately 1 in 6 couples globally, with male factors contributing to roughly half of these cases. Despite its prevalence, male infertility often remains under-discussed. Male fertility can often be sidelined, so together let’s shed light on the various causes of male infertility, in the hope of aiding awareness and understanding.

What Is Male Infertility?

Male infertility is when the quality, count, shape or production of sperm affects its ability to be used to fertilise an egg. This can be caused by an onslaught of factors, all of which we’ll uncover below. It’s important to note that male infertility is often treatable or even curable, depending on the underlying conditions. 

Common Causes of Male Infertility

Conception is a complex process, and several factors must align for pregnancy to occur. Male fertility plays a crucial role, and when one or more of these factors aren’t functioning properly, it can lead to difficulties. A range of health conditions and medical treatments, such as the following, can also contribute to male infertility.

1. Sperm Production Disorders

• Oligospermia (Low Sperm Count): A reduced number of sperm in the ejaculate can decrease the likelihood of fertilisation.

• Asthenozoospermia (Poor Sperm Motility): Sperm that cannot swim effectively may struggle to reach and fertilise the egg.

• Teratozoospermia (Abnormal Sperm Morphology): Sperm with irregular shapes may be less capable of fertilisation. Abnormal sperm may have two heads or two tails. In fact most sperm have abnormal morphology when you look at them down a microscope. We only need 4% of them to look normal. 

• Azoospermia: The complete absence of sperm in the ejaculate, which can be due to production issues or blockages.

2. Ejaculation disorders: These are disorders that men often feel embarrassed or shamed about. Some men get premature ejaculation, even sometimes before penetration, which can cause anxiety and frustration when trying to conceive. Others may have prolonged ejaculation or may not be able to ejaculate at all.

There are also times when men may actually be ejaculating backwards, and what we mean by that is that the sperm are going into the bladder rather than out into the semen (known as retrograde ejaculation). In these cases, sperm can be extracted from the urine for fertility treatment. 

3. Hormonal Imbalances

Hormones regulate sperm production. Testosterone is produced by the testes (balls inside a scrotum) after being signalled to do so by the pituitary gland. Therefore, if there is low testosterone, this will either be a problem of the testes themselves or the pituitary gland in the brain. Low levels can then interfere with sperm production.

4. Genetic Factors

Genetic conditions such as Klinefelter syndrome or Y chromosome microdeletions can affect sperm production and function. Cystic fibrosis is also a genetically inherited condition, and although sperm is produced normally in the testes, there is no pathway for the sperm to travel to be included in the semen.

5. Obstructions in the Reproductive Tract

Blockages in the tubes that transport sperm, such as the vas deferens, can prevent sperm from being present in the ejaculate. Causes include:

• Congenital Absence of the Vas Deferens: This is the muscular tube that transports the sperm from the epididymis to the urethra during ejaculation. It is the absence of this tube that is often associated with cystic fibrosis.

• Infections: Sexually transmitted infections, such as Chlamydia, can cause scarring and blockages.

• Surgical Procedures: Previous surgeries, like vasectomies, can obstruct sperm flow.

6. Varicocele

A varicocele is an enlargement of the veins within the scrotum, which can raise testicular temperature and affect sperm quality. 

7. Lifestyle and Environmental Factors

Certain habits and exposures can impact fertility:

• Smoking and Alcohol Consumption: Both can reduce sperm quality.

• Anabolic steroids: When you take anabolic steroids (these are synthetic versions of testosterone, which some men take to increase muscle mass when going to the gym), your body thinks that there is too much testosterone in your blood and reacts by telling your brain to reduce the hormones LH and FSH, which are essential for testosterone production. Vital to tell your doctor if you’re taking anabolic steroids. 

• Obesity: Excess weight can lead to hormonal imbalances, such as a decrease in the production of testosterone, which can affect sperm count, shape, and overall sperm production.

• Exposure to Toxins: Pesticides, heavy metals, and radiation can affect sperm production. Toxins such as these disrupt hormone production and create an imbalance between reactive oxygen species and the body’s ability to offset them with antioxidants. This can damage testicular tissue and may lead to decreased sperm count

• Heat Exposure: Frequent use of saunas or hot tubs can impair sperm production. Long or very frequent bicycle rides can also heat the scrotum, and it is important to also think of limiting the use of heated car seats. 

8. Medical Conditions and Treatments

Certain medical issues and their treatments can influence fertility:

• Cancer Treatments: Chemotherapy and radiation can damage sperm-producing cells.

• Infections: Mumps and other infections can lead to testicular damage.

• Medications: Some medications can impair sperm production.

Can Male Infertility Be Treated or Prevented?

While not all cases of male infertility can be reversed, many can be improved with medical support and lifestyle changes. Here’s what to know:

• Lifestyle changes, such as maintaining a healthy weight, eating a balanced diet, quitting smoking and drinking, and limiting exposure to toxins, may improve sperm health.

• Fertility supplements (like CoQ10 or targeted sperm support products) can help support sperm quality and function.

• Medications that affect fertility may be adjusted or paused under the guidance of a medical professional.

• Surgical options, like a small surgical procedure to remove the varicocele or sperm retrieval, may be considered in specific cases.

• Assisted reproductive technologies (ART) such as IVF can offer alternatives when natural conception is challenging.

When to Seek Medical Advice

General advice is to seek fertility advice if you are

• Under 35 years old and have been trying for 12 months. 

• 35-40 years old and have been trying for 6 months

• If you are over 40, it is a good idea to get advice even if it hasn’t been 6 months. 

When thinking of male factor infertility I would get help sooner if a man has a history of any of the factors we have described above in ‘Common causes of male factor infertility’.

Imagine trying to conceive for 3 years only to find that a semen sample has no sperm in it. Information is a key step to success. 

Conclusion

Male factor infertility is more common than we think it is. But the good news is that it is also far more treatable than people realise. Infertility does not have to be a blame game, it’s a journey that people go on as a team and identifying a problem is the first step to finding a solution. Infertility is also not a reflection of someone's masculinity but a medical condition and one where help is available to you.