Male infertility: causes and treatment options

When trying for a baby does not work out, many men search desperately for answers. Infertility does not just strain the relationship. It gnaws at self-image. The good news: male infertility is often treatable.

Many couples think of the woman first when getting pregnant does not happen. That is a misconception. In almost half of all cases, the cause lies entirely or partly with the man.

How common is male infertility

The numbers surprise many people: according to the guideline of the European Association of Urology (EAU), a male factor is involved in about half of all involuntarily childless couples. In about 20% of cases, the cause lies solely with the man.

Global trend: sperm quality is declining

The evidence is alarming. Between 1973 and 2011, the average sperm concentration in men in Western countries fell by just over half (52.4%). A follow-up analysis by the same research group with data through 2018 suggests that the decline is accelerating: for data from the year 2000 onward, it was 2.6% per year.

German data: a realistic picture

In Germany, according to the German Society of Urology, one in six couples is involuntarily childless and needs medical help. The EAU guideline gives a prevalence of about 15% for couples of reproductive age. Whether there is a cause on the man’s side only becomes clear through examination, above all the semen analysis.

The true number is probably higher. Many men avoid seeing an andrologist, often out of misplaced shame or lack of knowledge.

Age effect in men is underestimated

While a woman’s age is discussed intensively, many people overlook the age effect in men. Usually from around age 40, fertility also declines in men: fewer sperm are produced, and their ability to fertilize an egg may decrease. Genetic errors in sperm become more frequent, and the risk of miscarriage rises. The EAU guideline also lists an older age of the father as a risk factor.

Causes at a glance: table

The causes of male infertility are varied. The following distribution comes from a large andrological analysis of nearly 13,000 patients, which the EAU guideline cites:

Lifestyle, infections, medications, and environmental factors do not appear as a separate group in these statistics. In addition to another cause, however, they can worsen sperm quality.

The big unknown: idiopathic infertility

In about one in three to four men, no clear cause is found despite extensive testing. This is enormously frustrating for those affected. But there are treatment options here too.

Modern andrology is developing rapidly. What counts as an “unknown cause” today could be treatable tomorrow.

Hormonal causes

The male hormone system is a finely tuned orchestra. When it falls out of rhythm, fertility suffers. Hormonal disorders often take a physical and psychological toll on men.

Hypogonadotropic hypogonadism: when the signal is missing

The classic case: the brain and pituitary gland produce too few stimulating hormones (FSH and LH). The result: the testicles work at greatly reduced capacity or stop completely.

The causes are varied. Congenital syndromes such as Kallmann syndrome or acquired damage from tumors, trauma, or radiation therapy are possible causes. Abuse of anabolic steroids can also be behind it.

The good news: this form is usually very treatable. With targeted hormone therapy (hCG, supplemented by FSH if needed), sperm production can often be restarted.

Hypergonadotropic hypogonadism: when the testicles fail

Here the problem lies directly in the testicles. Despite sufficient signals from the brain, they produce no testosterone or too little. The stimulating hormones FSH and LH are elevated accordingly.

Typical causes are Klinefelter syndrome, testicular trauma, infections, or chemotherapy. According to the EAU guideline, hormone therapy does not help here. Even so, the situation is not hopeless: with micro-TESE (microdissection testicular sperm extraction), individual sperm can often still be retrieved.

Hyperprolactinemia: the overlooked hormone

Elevated prolactin suppresses the hormones that control the testicles, and with them testosterone production. Certain medications or benign tumors of the pituitary gland can be behind it. The symptoms are often subtle: decreasing libido, erectile dysfunction, sometimes even swelling of the breast glands.

Treatment is usually simple. Medications such as cabergoline or bromocriptine lower prolactin, or a medication that triggers it is stopped. Sperm quality often improves as well.

Thyroid: the underestimated influence

Both an overactive and an underactive thyroid can impair male fertility. That is why thyroid levels are part of the workup when symptoms point that way. Fortunately, thyroid disorders can usually be treated well.

Anatomical causes: varicocele and undescended testicles

Sometimes mechanical problems stand in the way of fertility. Andrologists can often see or feel these directly. That makes diagnosis easier and treatment usually promising.

Varicocele: the most common treatable cause

According to the EAU guideline, varicose veins at the testicle are found in almost 15% of all men, and in 35% to 40% of men with fertility problems. The enlarged veins cause blood to pool, raise the temperature in the scrotum, and can thereby harm the delicate process of sperm production.

Grades of varicocele and what they mean

There are three grades:

• Grade I: Palpable only when straining
• Grade II: Palpable at rest
• Grade III: Visible and palpable at rest

There is also the subclinical varicocele, which is only noticeable on ultrasound. Not every varicocele needs to be treated. What matters are symptoms and, above all, sperm quality. With poor values and a palpable varicocele, surgery is usually recommended. For a varicocele visible only on ultrasound, however, surgery showed no benefit in studies.

Surgical treatment: microscopically precise

Modern varicocele surgery is done microscopically. Under high magnification, only the affected veins are closed off, while arteries and lymphatic vessels are spared. According to the EAU guideline, there are fewer complications and recurrences than with other techniques.

The results are encouraging: in men with abnormal values, sperm values usually improve after surgery. It takes up to two cycles of sperm formation before this shows. In studies, a spontaneous pregnancy usually occurred six to twelve months after the procedure.

Undescended testicles: late effects of a childhood problem

Normally, the testicles descend from the abdomen into the scrotum during pregnancy. If one or both stay “up,” it is called cryptorchidism or undescended testicle.

Left untreated, the higher body temperature can lead to permanent damage, and the loss of germ cells begins as early as the first year of life. Even after successful treatment in childhood, reduced fertility often remains.

Unilateral vs. bilateral undescended testicles

With a unilateral undescended testicle, the healthy testicle often compensates well: according to the EAU guideline, almost as many of these men become fathers as men without an undescended testicle (89.7% versus 93.7%). It is different with bilateral undescended testicles: even after successful treatment, 75% have a reduced sperm count and 42% have no sperm at all in the ejaculate.

Those affected usually end up in an andrology consultation only as adults. By then, much has often already been decided for fertility. What matters is early treatment in childhood.

Other anatomical causes

Obstructions of the sperm ducts caused by infections or congenital malformations block the transport of sperm. Despite normal sperm production, no sperm or only a few are then found in the ejaculate.

TESE surgery can help here. In this procedure, sperm are taken directly from the testicle and used for ICSI treatment.

Genetic causes

Genetics plays a bigger role in male infertility than many people think. Genetic disorders that affect fertility are regularly found during the workup. Understanding these causes helps with counseling and treatment planning.

Klinefelter syndrome: the most common chromosomal cause

In Klinefelter syndrome, men have an extra X chromosome (47,XXY instead of 46,XY). It is the most common abnormality of the sex chromosomes. In a large andrological analysis, it affected 2.6% of all patients and 13.7% of men with no sperm in the ejaculate. Klinefelter syndrome is often the cause of severe oligozoospermia or complete azoospermia.

Typical features are small, firm testicles and signs of testosterone deficiency. The presentation varies widely, however.

Treatment options for Klinefelter syndrome

Testosterone production is usually reduced. Testosterone replacement therapy can relieve the symptoms of the deficiency but additionally suppresses sperm production, which is already limited.

For this reason, testosterone is avoided when trying to conceive. According to the EAU guideline, hormonal stimulation does not help in this form (primary hypogonadism). The most important option is a micro-TESE: it can retrieve sperm in up to 50% of cases.

Y chromosome deletions: when genes for fertility are missing

Small gaps in the Y chromosome can have major effects. Depending on the affected region (AZFa, AZFb, or AZFc), the spectrum ranges from severe oligozoospermia to complete azoospermia.

According to the EAU guideline, Y deletions are found in 8% to 12% of men with no sperm in the ejaculate and in 3% to 7% of men with a severely reduced sperm count. Diagnosis is simple: a blood test shows the deletion. Important for counseling: sons inherit the deletion from their father. With complete deletions that involve AZFa and AZFb, the chances are so poor that the guideline advises against TESE.

AZFc deletions: still hope for their own sperm

With AZFc deletions, sperm can still be found in the testicle in 50% to 75% of cases (by TESE). The prognosis is much better than with other deletions.

Particularly thorough genetic counseling is important for these men. The decision to pursue treatment affects not only them but also their potential sons.

Cystic fibrosis: not just a lung disease

Mutations in the CFTR gene cause not only cystic fibrosis but also congenital absence of the vas deferens (CAVD). Sperm production is normal, but transport is blocked.

According to the EAU guideline, bilateral absence of the vas deferens is found in about 1% of men with fertility problems. Around 4% of people of European descent carry a mutation in the CFTR gene. This has consequences for family planning: if the partner is also a carrier, the children can develop cystic fibrosis.

Other genetic causes

Robertsonian translocations and other chromosomal disorders can lead to recurrent miscarriages, even when fertilization succeeds. Genetic testing clarifies the cause.

Monogenic disorders such as mutations in genes for cilia proteins cause Kartagener syndrome, with immotile sperm. Diagnosis is becoming ever more precise. Treatment options remain limited, however.

Lifestyle factors

A modern lifestyle can considerably harm male fertility. The positive side: men can influence these factors themselves. Often all it takes is the right nudge and realistic goals.

Smoking: the enemy of sperm

The data are clear: smokers have poorer sperm quality. The concentration, motility, and shape of sperm suffer from tobacco use. Genetic material is also damaged.

A large meta-analysis of 20 studies with 5,865 participants confirms the link between smoking and poorer sperm values. On average, men who smoke produce fewer sperm, and more genetic damage is found in their semen.

What quitting smoking can do

Example: a 34-year-old man has smoked 40 cigarettes a day for 15 years, and his semen analysis is clearly impaired. Quitting removes an important disruptive factor. It takes patience, however, before this shows up in the results.

Quitting smoking is always worthwhile. Because new sperm take just over three months to mature, an improvement shows up in the semen analysis after about three months at the earliest.

Alcohol: moderation is what matters

According to a large meta-analysis, moderate alcohol consumption does not appear to worsen sperm values. It becomes a problem with regularly more than two drinks a day: large amounts of alcohol can lower testosterone levels and harm fertility.

The good news: according to familienplanung.de, the effects are usually reversible after stopping.

Overweight: more than a cosmetic problem

Obesity changes the hormone profile. Testosterone falls, estrogens rise. Excess weight can impair testicular function and reduce sperm production.

Mechanisms of overweight-related infertility

Fat tissue produces aromatase, an enzyme that converts testosterone to estrogen. This can result in a testosterone deficiency caused by excess weight.

Also under discussion are impaired temperature regulation in the scrotum, more inflammatory processes, and more oxidative stress. All of this can harm the delicate process of sperm production.

Weight loss as a success factor

Losing weight may improve sperm values, as observational studies suggest. The results of controlled studies, however, are contradictory. Even so, weight loss can improve a testosterone deficiency caused by excess weight. A combination of dietary changes and exercise makes sense.

Heat: the underestimated enemy

The testicles hang outside the body for a reason. For sperm formation, they need to stay about 2°C (3.6°F) cooler than normal body temperature, as consistently as possible. Overheating can impair sperm production.

Laptops on the lap, frequent sauna visits, tight underwear, or sedentary work can become a problem. According to the WHO, a recent febrile illness also affects the values in a semen analysis.

Stress: a burden on body and relationship

Whether stress directly worsens sperm quality has not been clearly settled scientifically. What is clear: being unable to conceive is itself a major burden for many couples, including for libido.

Relaxation techniques, exercise, or psychological counseling can help in coping better with the situation.

Diagnosis: semen analysis and beyond

Modern andrology goes far beyond the simple semen analysis. A multi-step diagnostic approach is standard and is expanded depending on the findings. The goal is to find the cause of infertility and to base treatment on it. Which options exist, from home tests to the fertility clinic, and what they show, is compared in the guide Male fertility test.

The semen analysis: the foundation of diagnosis

Every andrological examination begins with the semen analysis. After 2 to 7 days without ejaculation (according to the WHO), the sample is collected by masturbation, ideally at the practice, to avoid damage during transport.

The 2021 WHO reference values describe the lower 5th percentile of men whose partner became pregnant within a year:

• Volume: ≥ 1.4 ml
• Concentration: ≥ 16 million/ml
• Total number: ≥ 39 million per ejaculate
• Motility: ≥ 42% motile
• Morphology: ≥ 4% normally formed

Interpretation: more than just numbers

A poor semen analysis does not automatically mean infertility. Some couples get pregnant spontaneously despite dismal values. Conversely, good values do not guarantee fertility.

The overall picture is what matters. According to the WHO, the reference values are expressly not a dividing line between fertile and infertile. If the findings are abnormal, the semen analysis is usually repeated after 8 to 12 weeks, because values can vary widely from sample to sample.

Extended sperm testing

If the standard semen analysis is not enough, additional tests come into play:

DNA fragmentation: Measures damage to the genetic material of sperm. According to the EAU guideline, a share of 25% damaged sperm (measured with the SCSA test) is the threshold above which the chances of a pregnancy by natural conception or through IUI decline. Values above 50% are associated with poorer IVF results.

Acrosome reaction: Tests whether sperm can penetrate the outer layer of the egg. Abnormal reactions can provide clues in unexplained IVF failures.

Hypo-osmotic swelling test: Tests membrane integrity. Important with poor motility or before ICSI.

Hormone testing: the endocrine profile

Alongside the semen analysis, important hormones are measured:

• FSH and LH: Show whether stimulation of the testicles is working
• Testosterone: Best in the morning
• Prolactin: If hyperprolactinemia is suspected
• Thyroid hormones: TSH, T3, and T4 when symptoms point to a thyroid problem

Interpreting hormone levels

Elevated FSH points to damage to the testicles. Low FSH with a poor semen analysis suggests a hormonal cause, often well treatable.

Testosterone alone is not enough. Free or bioavailable testosterone matters too. SHBG (sex hormone-binding globulin) can considerably affect the interpretation.

Physical examination: the big picture

The examination begins with the overall impression: body build, body hair, and voice can provide clues to hormonal disorders. The genital examination is done standing and lying down.

Testicle size: In the general European population, testicles are on average about 20 ml in size (plus or minus 5 ml), measured with an orchidometer. According to the EAU guideline, there are no uniform normal values. Small testicles usually produce fewer sperm.

Consistency: Soft testicles can point to hormonal disorders, hard ones to tumors or scarring.

Epididymis: Hardened areas or cysts can obstruct the transport of sperm.

Varicocele diagnosis

The examination is done standing in a warm room. The spermatic cord is palpated systematically along its length while the patient bears down. Doppler ultrasound can help assess borderline findings more objectively.

Not every varicocele needs treatment. What matters are symptoms, testicle size, and above all sperm quality.

Further diagnostics

For specific questions, additional procedures help:

Genetic testing: According to the EAU guideline, a chromosome analysis (karyotype) for azoospermia or fewer than 10 million sperm per milliliter, a test for Y chromosome deletions at 1 million sperm per milliliter or fewer (to be considered below 5 million), and a CFTR analysis when the vas deferens is absent.

Transrectal ultrasound: If obstructions of the sperm ducts or cysts are suspected.

Testicular biopsy: Rarely needed anymore, usually directly as part of a TESE procedure.

Treatment options by cause

Treatment of male infertility depends on the underlying cause. Andrologists usually follow a stepwise approach: from the simplest to the most complex treatment. Patience is required: new sperm take just over three months to mature.

Hormonal treatments: often the first step

With secondary hypogonadism, that is, when the signal from the brain or pituitary gland is missing, the chances of success are good. If, on the other hand, the testicles themselves are damaged (primary hypogonadism), hormone therapy does not help, according to the EAU guideline.

Hypogonadotropic hypogonadism: stimulation instead of replacement

Instead of replacing testosterone, the body’s own production is stimulated. Human chorionic gonadotropin (hCG) mimics luteinizing hormone and stimulates testosterone and sperm production.

Typical approach according to the EAU guideline: start with 250 IU of hCG twice a week, increasing if needed to up to 2,000 IU twice a week. The semen analysis is checked every three months. If the effect is not enough, FSH is added; a combination from the start is also possible.

Clomiphene citrate: the classic stimulation drug

Clomiphene citrate is often used for mild hormonal disorders. It blocks estrogen receptors in the brain and thereby increases the body’s own FSH and LH production.

Clomiphene is not approved for men; it is used off-label. For men with unexplained impaired values, the EAU guideline sees no conclusive data for drugs such as clomiphene. It cites more evidence for FSH treatment when the FSH level is in the normal range.

Hyperprolactinemia: quick help with dopamine agonists

Elevated prolactin can usually be treated easily. Dopamine agonists such as cabergoline or bromocriptine lower the levels. If a medication is the trigger, it is stopped where possible. According to the EAU guideline, treatment can improve sperm quality.

Finding the cause is important: MRI when levels are markedly elevated.

Surgical treatments: correcting the anatomy

Mechanical problems usually require surgical correction. Success rates are good when the indication is right.

Varicocele surgery: the classic

Microscopic varicocele surgery can be done on an outpatient basis under local anesthesia. Through a small incision in the groin, the enlarged veins are closed off under the microscope.

Success rates: in men with a palpable varicocele and abnormal values, sperm values usually improve and the chance of pregnancy rises. A 2021 Cochrane review found a pregnancy rate that was higher by about half compared with no treatment or later treatment (relative risk 1.55).

Complications are rare: with microsurgery through the groin or below it, the recurrence rate according to the EAU guideline is 0.4%, and a collection of fluid in the scrotum (hydrocele) occurs in 0.44% of cases.

Obstructions of the sperm ducts: microsurgery needed

For obstructions of the epididymis or vas deferens, microsurgical reconstruction is an option. The operation is demanding but successful when the indication is good.

Vasoepididymostomy: connection between the epididymis and the vas deferens. According to the EAU guideline, patency: 63% to 85%, natural pregnancy: 21% to 45%.

Vasovasostomy: reversal after vasectomy. Patency: 90% to 97%, pregnancy: 52% to 73%.

Antibiotic treatment: for confirmed infections

Bacterial infections of the prostate or epididymis can impair fertility. Antibiotics can improve sperm quality. However, according to the EAU guideline, it has not been shown that treating chronic prostatitis increases the chance of a natural pregnancy.

Possible pathogens include chlamydia, for example. Which antibiotic is given and for how long depends on the pathogen.

Antioxidant therapy: a supplement to the main treatment

Oxidative stress damages sperm. Antioxidants may improve sperm values but are never the sole treatment. According to the EAU guideline, there are no conclusive data on which active ingredients help at which dose. In the large MOXI study, antioxidants improved neither sperm values nor DNA quality.

Combinations of the following are usually used:

• Vitamin E
• Vitamin C
• Coenzyme Q10
• Selenium
• Zinc

More is not better here: stick to the maximum amounts for dietary supplements and discuss the dosage with your doctor. Taking them for at least three months makes sense, because new sperm take that long to mature.

Reproductive medicine procedures

If conservative measures are not enough, reproductive medicine procedures come into play. The choice depends on the severity of the disorder.

IUI: the gentle first step

For mild to moderate disorders of sperm quality, intrauterine insemination (IUI) is an option. Prepared sperm are flushed directly into the uterus.

Requirements: enough motile sperm after preparation, open fallopian tubes, and a partner who is able to ovulate.

Success rates: according to the German IVF Registry (Deutsches IVF-Register, D.I.R.), 10.3% of inseminations with partner sperm in 2024 led to a clinical pregnancy, and the live birth rate in 2023 was 6.3% per insemination. The costs are manageable. The burden is low.

IVF/ICSI: the next level

For severe disorders, there is no way around IVF or ICSI. ICSI is usually the method of choice in male infertility: a single sperm is injected directly into the egg.

Conclusion

Male infertility is common: a male factor is involved in about half of all involuntarily childless couples. The semen analysis comes first in the workup, supplemented by hormone levels, a physical examination, and genetic tests if needed. Many causes, such as a varicocele or secondary hypogonadism, can be treated in a targeted way, and a healthier lifestyle can improve values further. Even when there is no sperm in the ejaculate, TESE and ICSI often still offer a path to a child of your own. If you want to know where to start, our Fertility Clinic Finder can help.

Sources

• Temporal trends in sperm count: a systematic review and meta-regression analysis, Human Reproduction Update (Levine et al.), 2017
• WHO laboratory manual for the examination and processing of human semen, 6th edition, World Health Organization, 2021
• EAU Guidelines on Sexual and Reproductive Health: Male Infertility, European Association of Urology, 2026
• DGA, DGU, and BvDU define standards for the diagnosis of male infertility, German Society of Urology, 2024
• Fertility disorders in men: physical causes, familienplanung.de (Federal Institute for Public Health), 2026
• Age, lifestyle, and environment: many factors affect fertility, familienplanung.de (Federal Institute for Public Health), 2026
• Sperm and male fertility, familienplanung.de (Federal Institute for Public Health), 2026
• Male reproductive organs, familienplanung.de (Federal Institute for Public Health), 2026
• Diseases and fertility disorders in men, Fertility Information Portal (Informationsportal Kinderwunsch, BMFSFJ), retrieved 2026
• D·I·R Yearbook 2024, German IVF Registry, 2025