Male Infertility: Causes, Symptoms, Diagnosis & Treatment

Infertility is traditionally understood as a shared journey between partners, yet for decades conversations focused predominantly on women’s health. Modern reproductive medicine paints a different picture: male factors contribute to approximately 40–50% of infertility cases, either alone or together with female factors.

Despite its prevalence, male infertility remains surrounded by misconceptions. Many men equate fertility with sexual performance, assuming that normal libido and healthy erections guarantee natural fertility. In reality, sperm production, sperm quality, and hormonal regulation are complex biological systems that are not directly reflected by erectile function.

The encouraging reality is that male fertility problems can often be identified and, depending on the cause, treated effectively. Advances in diagnostics, microsurgery, and assisted reproductive technology have created multiple pathways to parenthood.

Male infertility refers to factors in the male partner that reduce the likelihood of pregnancy after 12 months of regular, unprotected intercourse. Conception requires a sequence of events: healthy sperm production, an adequate count and motility, unobstructed passage through the epididymis and vas deferens, and effective delivery into the female reproductive tract.

In many cases male infertility causes no obvious symptoms — erections, ejaculation, and libido remain normal. When symptoms do occur, they may include ejaculatory difficulties (reduced volume, retrograde or delayed ejaculation), testicular pain, swelling, or a mass, signs of varicocele (a "bag of worms" appearance), hormonal signs (reduced body hair, gynecomastia, reduced libido), recurrent respiratory infections (sometimes linked to cystic fibrosis), or a reduced sense of smell (which can point to Kallmann syndrome).

Problems with sperm production or maturation inside the testicles are among the leading causes of male infertility: low concentration (oligospermia, below the WHO limit of 16 million/mL), a complete absence of sperm (azoospermia), poor motility, or abnormal morphology.

Varicocele — an enlargement of veins around the testicle, similar to varicose veins in the legs — can raise scrotal temperature and oxidative stress, negatively affecting sperm count, motility, and DNA integrity. Undescended testicles (cryptorchidism) can also impair sperm production because of higher abdominal or groin temperatures.

Sperm production is controlled by the brain–pituitary–testicle axis. Primary hypogonadism means the testicles themselves cannot produce enough testosterone; secondary hypogonadism means the pituitary provides insufficient LH or FSH stimulation. Thyroid disorders, elevated prolactin, and other endocrine conditions can also play a role.

Chromosomal and genetic conditions include Klinefelter syndrome (47,XXY — leading to underdeveloped testicles, low testosterone, and severe oligospermia or azoospermia), Y-chromosome microdeletions (missing DNA segments important for sperm production), and congenital bilateral absence of the vas deferens (frequently linked to the CFTR gene, also associated with cystic fibrosis).

Even when sperm production is normal, a physical blockage or an ejaculatory problem can prevent sperm from reaching the ejaculate: ductal obstruction from prior infections, injury, surgery, or congenital causes; retrograde ejaculation, in which semen enters the bladder instead of exiting the penis (from diabetes, nerve damage, certain medications, or pelvic surgery); or severe erectile or ejaculatory dysfunction.

Lifestyle and environmental factors also affect semen quality: smoking, heavy alcohol and recreational drug use, anabolic steroids, repeated heat exposure (saunas, hot tubs), pesticides, industrial solvents and heavy metals, obesity and metabolic disorders, and chronic stress.

A thorough evaluation includes: a medical history (childhood illnesses including post-pubertal mumps, previous surgeries, testicular development, lifestyle, medications, prior cancer treatment, and environmental exposures); a semen analysis (the cornerstone test, often repeated); hormonal blood tests (total testosterone, FSH, LH, and, when indicated, prolactin and TSH); a scrotal ultrasound (used when clinically indicated, not routine for everyone); and, for severe oligospermia or azoospermia, genetic testing (karyotyping, Y-chromosome microdeletion testing, CFTR gene testing).

WHO 6th-edition lower reference values: semen volume ≥1.4 mL, concentration ≥16 million/mL, total count ≥39 million, total motility ≥42%, progressive motility ≥30%, normal morphology ≥4%.

Treatment depends on the cause, severity, the couple’s reproductive goals, and the female partner’s fertility.

Lifestyle changes — quitting smoking and drugs, limiting alcohol, maintaining a healthy weight, avoiding excessive heat, and managing chronic conditions; effects generally take several months.

Medication and hormonal treatment — hCG and, when indicated, FSH may be used in hypogonadotropic hypogonadism; antibiotics only for a confirmed infection; and treatment for erectile or ejaculatory dysfunction. Important: testosterone replacement therapy is generally not used to treat infertility, since it suppresses the body’s own LH and FSH production.

Varicocele surgery — microsurgical varicocelectomy may improve semen parameters in appropriately selected men with a clinically significant varicocele.

Sperm retrieval — TESE/micro-TESE (from testicular tissue) or PESA/MESA (from the epididymis) for azoospermia.

ART — intrauterine insemination (IUI) for mild cases; IVF with ICSI for severe male-factor infertility or surgically retrieved sperm.

Can male infertility be cured? It depends on the cause. Some causes — hormonal disorders, infections, varicocele, obstruction — can be treated effectively. In other cases, treatment focuses on improving the chance of conception through sperm retrieval and IVF with ICSI.

Can a man with zero sperm count have biological children? In some cases, yes. In obstructive azoospermia, production is preserved; in non-obstructive azoospermia, sperm can sometimes be retrieved via micro-TESE.

Does low testosterone mean a low sperm count? Not necessarily — they are related but distinct measures of reproductive function. However, testosterone replacement therapy can significantly reduce sperm counts.

When should you see a fertility specialist? After 12 months of regular, unsuccessful attempts to conceive; after 6 months if the female partner is 35 or older; sooner if there are known risk factors (testicular trauma, surgery, varicocele, testosterone/steroid use, prior chemotherapy or radiation).