Male Infertility Causes: What Can Affect Sperm and Fertility

How often the male partner is involved

Estimates depend on how the numbers are counted. The AUA guideline, written with ASRM, states that infertility is due in whole or in part to the male in approximately one-half of all infertile couples, and it notes that the true prevalence of male infertility is not clearly defined because definitions and study populations vary. MedlinePlus says about a third of the time, infertility is because of a problem with the man. The National Institute of Child Health and Human Development (NICHD) puts it simply: problems in the male are just as likely as problems in the female.

NICHD also notes that causes can be multiple and overlapping, and that in many cases the exact cause remains unknown or unexplained. A normal result in one partner does not close the question for the couple.

Problems with sperm production

NICHD says many different issues can affect the formation of sperm in the testicles, and that problems with testicular function are the most common cause. They can lead to abnormal sperm or low sperm counts.

The most common cause of oligospermia (a low sperm count), according to NICHD, is varicocele. In a varicocele, enlarged veins disrupt blood flow in the testicle and cause an increase in temperature, which affects sperm production. MedlinePlus also lists physical problems with the testicles and past high fevers or mumps among the causes.

Hormone problems

NICHD lists hormone imbalances, such as overproduction of prolactin, insensitivity to hormones called androgens (which include testosterone), and thyroid problems as possible causes.

The blood tests NICHD lists for a male evaluation include testosterone, follicle-stimulating hormone (FSH), thyroid hormones, and prolactin.

Genetic conditions

NICHD lists chromosome defects as a cause, including the chromosome disorder Klinefelter syndrome, as well as genetic disorders more broadly in MedlinePlus. When few or no sperm are found, a provider may test for chromosome abnormalities before fertility treatments begin.

Blockages and ejaculation problems

Sperm have to travel from the testicles to the penis through a series of tubes. NICHD says natural blockages in those tubes can prevent sperm from being transported, and a vasectomy can also cause it. MedlinePlus lists blocked sperm ducts among the causes. The AUA guideline's scope includes obstructive azoospermia (no sperm in the semen because of a blockage), including after a vasectomy.

NICHD also describes retrograde ejaculation, in which sperm move into the bladder, and notes that some medications increase the likelihood of this problem.

Medications, including testosterone

Several kinds of medicine can reduce sperm production. NICHD says taking multiple medications is known to reduce sperm count, and that body-building medications or androgens can affect sperm formation.

This includes testosterone prescribed for low testosterone. The FDA label for AndroGel states that with large doses of exogenous androgens, spermatogenesis may be suppressed through feedback inhibition of pituitary FSH, possibly leading to adverse effects on semen parameters including sperm count. The label adds that reduced fertility is observed in some men taking testosterone replacement therapy. If you take testosterone or any body-building product and are trying to conceive, tell your clinician before you do anything else, and do not stop a prescription on your own.

Lifestyle and environment

NICHD's page on lifestyle and environmental factors links several of them to male fertility:

• Obesity is linked to lower sperm count and quality in men.
• Strenuous physical labor and taking multiple medications are known to reduce sperm count.
• Substance use, including smoking tobacco, using other tobacco products, marijuana use, and heavy drinking, can reduce fertility, and the page names heroin and cocaine.
• High blood pressure changes the shape of sperm.
• Endocrine-disrupting chemicals in the environment can affect male and female fertility.

The same page says the type of underwear a man chooses is not related to his infertility. It also says that in males, age is known to reduce the quality of sperm, and that men produce fewer sperm as they age.

Treat these as factors that can contribute, not as a way to assign blame.

How male infertility is evaluated

According to NICHD, the evaluation starts with a history and a physical exam. The history covers past injury to the testicles or penis, recent high fevers, and childhood diseases such as mumps. The exam of the testes and penis can identify infection, hernia, malformed sperm tubes, hormone deficiency, masses, and varicocele.

The core test is a semen analysis. NICHD says the man is asked to abstain from ejaculation for about 48 hours beforehand, and that more than one sample may be needed because sperm production can vary over time with health, activity, and stress. Our guide to at-home semen analysis explains what it measures and how kits work. Beyond that, a provider may order hormone blood tests, genetic testing when few or no sperm are found, and in some cases a testicular biopsy to extract sperm.

The AUA/ASRM guideline also makes a point that goes beyond fertility: the detection of male infertility increases the risk of subsequent health problems for men, and specific medical conditions are associated with some causes. That is one more reason to be evaluated rather than to assume.

When a reproductive urologist helps

Some causes are best treated in person. The AUA guideline covers treatments such as varicocele repair and sperm retrieval, and MedlinePlus says treatments may include medicines, surgery, or assisted reproductive technology. A reproductive urologist is the specialist who evaluates and treats these. If you are unsure when to start testing at all, see how long to try before testing.

How male testing works at Gala

At Gala Fertility, testing covers both partners. After one shared intake, his semen analysis is done with a kit sent to his home, and, if your clinician indicates it, he gets bloodwork at a Quest lab for FSH, LH, TSH, total and free testosterone, and SHBG. Your clinician reviews every result and explains it on one video visit. Some findings are best treated in person, such as certain semen results. If yours is one of them, your clinician refers you to a fertility clinic or a reproductive urologist and explains why.

Gala Fertility is for male-female couples trying to conceive, both 18 or older, and is not available in New York, New Jersey, or Rhode Island. IUI, IVF, and other in-person care after a referral are not included. Read more about the male fertility test and fertility testing for couples, or start your fertility intake together.

This article is general education, not medical advice. Talk to a clinician about your own results.

Sources

1. American Urological Association. Male infertility guideline (AUA/ASRM, published 2020, amended 2024).
2. Schlegel PN, et al. Diagnosis and treatment of infertility in men: AUA/ASRM guideline part I. Fertil Steril. 2021.
3. NICHD, NIH. What causes infertility?
4. NICHD, NIH. What are the possible causes of male infertility?
5. NICHD, NIH. What lifestyle and environmental factors may be involved with infertility in females and males?
6. NICHD, NIH. What age-related factors may be involved with infertility in females and males?
7. NICHD, NIH. How do health care providers diagnose infertility?
8. MedlinePlus. Male infertility. National Library of Medicine.
9. Ascend Therapeutics / NLM DailyMed. AndroGel 1.62% prescribing information.

This article is for general information and is not medical advice. Talk to a licensed provider about your own health.