Testicular atrophy

Quick takeaways

• Testicular atrophy is a true reduction in testicle size caused by loss of tissue—not just temporary tightening from temperature or anxiety.
• It may be linked to low testosterone, poor sperm production, infertility, infection, varicocele, steroid use, injury, or reduced blood flow.
• One-sided atrophy and sudden pain need prompt medical evaluation, especially if testicular torsion is possible.
• A doctor may use a physical exam, scrotal ultrasound, hormone testing, and sometimes semen analysis to find the cause.
• Anabolic steroid or testosterone use can shrink the testicles by suppressing the body’s own hormone signaling.
• Some causes are reversible or partly reversible; others may cause permanent changes if not treated early.
• If you are trying to conceive, testicular atrophy should not be ignored, because it can affect sperm count, sperm quality, and hormone balance.
• Persistent changes in testicle size, firmness, pain, or a lump should be assessed by a clinician.

What does testicular atrophy mean?

The testicles have two main jobs:

• make testosterone, the main male sex hormone
• produce sperm inside tiny structures called seminiferous tubules

When testicular atrophy happens, the tissue involved in one or both of these functions becomes reduced. That reduction can happen for several reasons:

• hormonal suppression
• damage from infection, inflammation, or trauma
• poor blood flow
• long-term heat stress or varicocele
• genetic or developmental conditions
• aging-related changes

Some men notice one testicle looks smaller than the other. Mild asymmetry can be normal, but a progressive decrease in size, especially with pain, fertility problems, or symptoms of low testosterone, deserves attention.

Why testicular atrophy matters in men’s health and fertility

Testicular atrophy is important because the testicles are central to male reproductive and hormonal health. If the testes are shrinking due to damage or hormonal suppression, the effects can extend beyond appearance.

Potential consequences include:

• Reduced sperm production, sometimes leading to low sperm count or no sperm in the ejaculate
• Lower testosterone, which may affect mood, energy, libido, erections, muscle mass, and body composition
• Impaired fertility, especially when both testicles are affected
• Underlying disease, such as varicocele, mumps orchitis, a pituitary problem, or testicular torsion
• Psychological distress, including body-image concerns and anxiety about sexual or reproductive health

Not every smaller testicle means severe dysfunction. Some men maintain normal hormone levels and fertility. But because testicular size is often linked to testicular function, meaningful shrinkage should not be dismissed.

Common causes of testicular atrophy

There is no single cause of testicular atrophy. The most common causes range from hormone-related suppression to direct damage of testicular tissue.

1. Anabolic steroids or external testosterone use

This is one of the best-known causes. When someone uses anabolic steroids or testosterone replacement, the brain senses enough androgen in circulation and reduces production of luteinizing hormone (LH) and follicle-stimulating hormone (FSH). Without that stimulation, the testicles make less testosterone internally and sperm production falls. Over time, the testicles may shrink.

This type of atrophy may be partly reversible in some men after stopping use, but recovery is variable and can take months or longer.

2. Varicocele

A varicocele is an enlargement of the veins in the scrotum, often described as feeling like a “bag of worms.” It is a common and treatable cause of impaired sperm quality and can be associated with a smaller testicle, especially on the left side. Theories include increased scrotal temperature, oxidative stress, and altered blood flow.

3. Testicular torsion

Testicular torsion happens when the spermatic cord twists and cuts off blood supply to the testicle. It causes sudden, severe scrotal pain and is a medical emergency. Even if the testicle is saved, delayed treatment can lead to permanent damage and later atrophy.

4. Orchitis and infections

Orchitis means inflammation of the testicle. It can occur due to viral or bacterial infection. Mumps orchitis is a classic example and can lead to testicular shrinkage after the acute infection resolves. Some sexually transmitted infections or epididymo-orchitis cases may also damage the testicle if severe or untreated.

5. Aging and gradual testicular decline

Testicular changes can occur with age, though aging alone is not usually the only factor. Some decline in testicular function may happen over time, especially when combined with chronic illness, vascular disease, obesity, or medications.

6. Undescended testicle (cryptorchidism)

If a testicle did not descend normally during infancy or childhood, it may be smaller and function less well later in life. Even after surgical correction, fertility potential may be reduced depending on timing and severity.

7. Trauma or injury

Blunt injury to the scrotum can damage testicular tissue or blood supply. Severe trauma may lead to scarring and shrinkage over time.

8. Hormonal or pituitary disorders

The testicles depend on signals from the brain—mainly LH and FSH from the pituitary gland. Conditions that reduce these signals, such as pituitary disease or some forms of hypogonadism, can contribute to smaller testes and reduced sperm production.

9. Chemotherapy, radiation, or toxic exposures

Cancer treatments can damage sperm-producing cells and hormone-producing cells. Certain environmental or occupational exposures may also affect testicular function, though risk varies by substance and dose.

10. Genetic conditions

Some inherited conditions are associated with small testes and reduced fertility. One example is Klinefelter syndrome, in which men often have small, firm testicles and impaired sperm production.

11. Chronic heavy alcohol use or liver disease

Heavy alcohol use and advanced liver disease may disrupt hormone balance and contribute to testicular shrinkage in some men.

Causes of testicular atrophy at a glance

Symptoms and signs of testicular atrophy

Some men notice no symptoms at all until fertility testing or a physical exam. Others notice clear changes.

Possible signs include:

• one or both testicles looking or feeling smaller
• a softer or less full-feeling testicle
• testicular pain, aching, or discomfort
• a heavy feeling in the scrotum
• reduced libido
• erectile difficulties
• fatigue or low energy
• loss of muscle mass or increased body fat
• difficulty conceiving
• lower semen volume or abnormal semen analysis results

Symptoms depend on the cause. For example, torsion usually causes sudden major pain, while steroid-related shrinkage may happen more gradually and with fertility changes. Varicocele may cause a dull ache or no symptoms at all.

What’s normal vs what’s not?

Many men worry because one testicle hangs lower or feels slightly different. Mild asymmetry is common. What raises concern is a real change in size, firmness, or function.

Normal findings can include:

• one testicle sitting slightly lower than the other
• small natural differences in size
• temporary shrinking or tightening in cold temperatures

Concerning findings can include:

• a testicle becoming noticeably smaller over time
• painful shrinkage
• a testicle that feels abnormally soft or, in some conditions, very firm
• a new lump, swelling, or persistent ache
• shrinking after steroid use, infection, or scrotal injury
• testicular asymmetry with infertility or low testosterone symptoms

How testicular atrophy is diagnosed

Diagnosis starts with confirming whether there is true atrophy and then identifying the cause. A clinician may evaluate both size and function.

Typical evaluation may include:

1. Medical history
   Symptoms, fertility goals, testosterone use, anabolic steroid use, infections, childhood undescended testicle, injury, cancer treatment, or prior surgery.
2. Physical examination
   Assessment of testicle size, consistency, tenderness, scrotal veins, and any mass or asymmetry.
3. Scrotal ultrasound
   This is often the best imaging test to measure testicular volume and look for varicocele, torsion-related damage, masses, or structural abnormalities.
4. Blood tests
   These may include total testosterone, free testosterone, LH, FSH, estradiol, prolactin, and sometimes other endocrine markers depending on the case.
5. Semen analysis
   If fertility is a concern, semen testing can assess sperm count, motility, morphology, and ejaculate volume.
6. Additional testing when needed
   Genetic testing, pituitary imaging, infectious workup, or tumor markers may be considered in selected cases.

Why ultrasound is often important

A scrotal ultrasound can help distinguish between simple asymmetry, true testicular volume loss, a varicocele, a mass, or signs of prior injury. It is useful when the cause is not clear from the exam alone.

Tests commonly used when testicular atrophy is suspected

How testicular atrophy affects sperm and fertility

Because sperm are made in the testicles, testicular atrophy can be closely tied to male fertility. The degree of impact depends on:

• whether one or both testicles are affected
• the underlying cause
• how long the problem has been present
• whether testosterone production is also affected

Possible fertility effects include:

• Low sperm count or severe oligospermia
• Poor sperm motility
• Abnormal sperm morphology
• Azoospermia, meaning no sperm in the ejaculate
• Hormonal patterns suggesting impaired sperm production

One healthy testicle can sometimes maintain adequate testosterone and sperm production, but this is not guaranteed. If you are trying to conceive and notice a smaller testicle, semen analysis is often one of the most useful next steps.

Important note on testosterone therapy and fertility

A common misconception is that testosterone therapy improves fertility because testosterone is the “male hormone.” In reality, external testosterone can suppress sperm production and contribute to testicular shrinkage. Men who want future fertility should discuss this carefully with a qualified clinician before starting treatment.

Treatment and management options

Treatment depends entirely on the cause. There is no single medication that fixes all cases of testicular atrophy.

Common treatment approaches

• Stopping anabolic steroids or reviewing testosterone therapy
  If hormone suppression is the cause, a specialist may discuss stopping the triggering agent or using fertility-preserving alternatives in selected cases.
• Treating varicocele
  Varicocele repair may be considered when there is pain, testicular atrophy, or infertility with abnormal semen parameters.
• Urgent treatment for torsion
  This requires emergency care and usually surgery. Time matters greatly.
• Treating infection or inflammation
  Bacterial causes may need antibiotics; supportive care may be used for viral causes. Early treatment may reduce complications.
• Addressing hormonal disorders
  Pituitary or endocrine conditions may need targeted treatment.
• Fertility support
  This may include semen analysis monitoring, referral to a reproductive urologist, sperm banking, or assisted reproductive techniques if needed.

If fertility is a priority

Men trying to conceive should consider discussing:

• baseline semen analysis
• reproductive hormone testing
• whether current medications affect sperm production
• timing of treatment relative to conception goals
• sperm banking if fertility may decline further

Can testicular atrophy be reversed?

Sometimes, but not always. Reversibility depends on what caused the shrinkage and how much tissue damage has already occurred.

Cases that may improve

• steroid- or testosterone-related suppression
• some varicoceles after treatment
• some endocrine causes after correcting the hormone issue

Cases that may be only partly reversible or permanent

• delayed treatment after testicular torsion
• severe mumps orchitis or other damaging infections
• significant trauma
• genetic disorders
• certain chemotherapy- or radiation-related injuries

Even when testicle size does not fully return, hormone function or fertility may still improve with the right treatment. The reverse is also true: normal-looking size does not always mean normal sperm production. That is why objective testing matters.

Lifestyle factors and prevention

Not all cases can be prevented, but some practical steps may reduce risk or help protect reproductive health.

Helpful habits

• avoid anabolic steroid misuse
• review testosterone use with a fertility-aware clinician
• seek prompt care for sudden scrotal pain
• treat sexually transmitted infections and scrotal infections early
• address a suspected varicocele if there is pain, shrinkage, or infertility
• limit heavy alcohol use
• protect the groin during sports and high-impact activity
• follow up after childhood history of undescended testicle if advised

What about heat, tight underwear, or hot tubs?

Frequent heat exposure can affect sperm production, but it does not usually cause obvious, permanent testicular atrophy by itself in healthy men. Tight underwear is not generally considered a major cause of true atrophy. Still, long-term scrotal heat stress may matter more in men who already have fertility issues.

Common myths about testicular atrophy

Myth: Smaller testicles always mean infertility

False. Smaller testes can be associated with reduced sperm production, but fertility cannot be judged by appearance alone. Some men with asymmetry remain fertile; others with normal-sized testes may have abnormal semen analysis.

Myth: Testosterone therapy boosts fertility

False in many cases. External testosterone often suppresses sperm production and can shrink the testicles.

Myth: Any difference in size is abnormal

False. Mild asymmetry is common. Progressive change, pain, or new firmness is more concerning.

Myth: If there is no pain, it is harmless

False. Varicocele, hormonal disorders, and steroid-related suppression may cause little or no pain while still affecting fertility and hormone status.

Questions to ask your doctor

• Do I have true testicular atrophy, or is this normal asymmetry?
• Should I get a scrotal ultrasound?
• Do I need testosterone, LH, FSH, or other hormone tests?
• Could any medication or supplement I use be contributing?
• Should I have a semen analysis if I want children?
• Is a varicocele present, and if so, does it need treatment?
• Is the cause likely reversible?
• Would seeing a urologist or reproductive urologist help?
• Should I bank sperm before treatment if fertility is at risk?

Related terms and tests

• Hypogonadism: low testosterone production or impaired testicular hormone function
• Varicocele: enlarged scrotal veins linked to infertility and sometimes testicular shrinkage
• Orchitis: inflammation of the testicle
• Testicular torsion: twisting of the spermatic cord causing impaired blood flow
• Semen analysis: a lab test that evaluates sperm count, motility, morphology, and volume
• FSH and LH: pituitary hormones that help regulate testicular function
• Total testosterone: a key blood test for androgen status
• Scrotal ultrasound: the main imaging test for testicular size and structure

When to seek medical care urgently

Get urgent medical help if you have:

• sudden severe testicular or scrotal pain
• rapid swelling
• nausea or vomiting with acute scrotal pain
• a high-riding or unusually positioned testicle
• pain after injury that does not improve

These symptoms can occur with testicular torsion, which is a time-sensitive emergency.

Schedule a non-emergency medical evaluation if you notice:

• a testicle that appears smaller over time
• persistent aching or heaviness
• low libido, fatigue, or other symptoms of low testosterone
• difficulty conceiving
• a lump or firmness change

Frequently asked questions

Can testicular atrophy happen on just one side?

Yes. Unilateral testicular atrophy can happen with varicocele, prior torsion, infection, trauma, or developmental issues. One-sided shrinkage still deserves evaluation.

Does testicular atrophy always lower testosterone?

No. Some men, especially if only one testicle is affected, may maintain normal testosterone levels. Others may develop low testosterone symptoms and abnormal lab results.

Can testicular atrophy cause infertility?

It can. Reduced testicular volume may reflect impaired sperm production, but the actual impact should be checked with a semen analysis and hormone testing.

Can masturbation cause testicular atrophy?

No. Masturbation does not cause true testicular atrophy.

Can testosterone replacement therapy shrink the testicles?

Yes. External testosterone can suppress LH and FSH, lower intratesticular testosterone, reduce sperm production, and cause the testicles to become smaller.

Is testicular atrophy painful?

Sometimes. It may be painless, or it may occur with aching, heaviness, or tenderness depending on the cause. Sudden severe pain is especially concerning.

Will testicle size come back after stopping steroids?

It may improve in some men, but recovery is unpredictable and can take time. Hormone and fertility recovery should be monitored by a clinician, ideally one experienced in male reproductive health.

How is testicular atrophy confirmed?

Usually through a combination of medical history, physical examination, and scrotal ultrasound. Hormone tests and semen analysis may also be important.

Does a smaller testicle mean cancer?

Not usually. Testicular cancer more often presents as a lump, firmness, or swelling rather than shrinkage alone. Still, any persistent change should be evaluated.

What kind of doctor treats testicular atrophy?

A primary care doctor can start the evaluation, but many men benefit from seeing a urologist or reproductive urologist, especially if fertility is a concern.

References

• American Urological Association (AUA) guidelines and patient resources on male infertility, testosterone deficiency, and acute scrotum.
• American Society for Reproductive Medicine (ASRM) committee opinions and guidance on male infertility evaluation and management.
• European Association of Urology (EAU) Guidelines on Sexual and Reproductive Health.
• Urology Care Foundation resources on testicular conditions, varicocele, and male fertility.
• National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) resources on testicular disorders and hypogonadism.
• Merck Manual Professional Edition entries on testicular torsion, orchitis, varicocele, and male hypogonadism.
• Peer-reviewed reviews in journals such as Fertility and Sterility, Human Reproduction Update, and Journal of Urology covering varicocele, testicular function, and fertility-related hormonal suppression.