Testicles grow rapidly during puberty and reach their peak size somewhere around age 30, after which they gradually shrink over the remaining decades of life. The actual testicular tissue does not get bigger with age. What does change is the scrotum and the tissues surrounding the testicles, and several common medical conditions can cause noticeable swelling that mimics an increase in testicular size. The distinction between what is happening to the testicle itself and what is happening to the scrotal sac around it is where most of the confusion lives.
Growth Peaks in Your Late Twenties
Testicular growth begins at puberty and continues for longer than most people realize. A study using imaging to track testicular volume in adolescents and young adults found that both size and metabolic activity increased steadily from puberty onset and continued rising until roughly age 30, with volume growing at a rate about ten times greater than metabolic activity over that span.1Journal of Nuclear Medicine. The testicular metabolic and volumetric changes in the adolescent and young adults Adult testicular volume in healthy men typically falls in a range of about 10 to 21 milliliters per testicle, with most men clustering between 15 and 21 milliliters.2PubMed Central. Appraisal of testicular volumes: volumes matching ultrasound values referenced to stages of genital development There is wide natural variation even among men of the same age, so comparing yourself to someone else is not particularly informative.
The Slow Shrink After Midlife
Once you pass the peak, testicular volume begins a long, gradual decline. An ultrasound study comparing healthy elderly men (median age 78) to young men (median age around 27) found that the older group had a combined bilateral testicular volume of about 21 milliliters compared to roughly 30 milliliters in the younger group.3The Journal of Clinical Endocrinology & Metabolism. Testicular Volume in Relation to Hormonal Indices of Gonadal Function in Community-Dwelling Elderly Men An earlier clinical study reported that testicular length was reduced in about three-quarters of men over 60, and volume was reduced in more than a third of them.4The American Journal of Medicine. Declining testicular function with age: Hormonal and clinical correlates
That said, the timing varies a lot between individuals. One large study found that when men with diseases known to shrink the testicles were removed from the analysis, the effect of age alone only became clear in the eighth decade of life, meaning after 70.5PubMed. Testicular size: the effects of aging, malnutrition, and illness So for many healthy men, any loss in testicular volume before their 70s may be subtle enough that they never notice it. The takeaway is that age-related shrinkage is real, but it is slow and does not hit everyone at the same pace.
What Happens Inside an Aging Testicle
The shrinkage is not just the testicle deflating uniformly. A range of structural changes accumulates over the years. The tubes where sperm are produced get shorter and narrower, and the cells responsible for making sperm gradually die off. The tissue around those tubes gets stiffer as collagen replaces functional tissue, and the outer capsule of the testicle thickens. Blood flow decreases as small vessels become partially blocked.6PubMed Central. Testicular ageing as a central hallmark of male senescence: characteristics, molecular mechanisms and emerging therapeutic strategies All of this adds up to a testicle that is both smaller and less efficient at doing its two main jobs: producing sperm and producing testosterone.
The hormonal side of this is worth understanding because it feeds back into the size question. As men age, the testicles produce less testosterone per unit of stimulation from the brain’s hormonal signals. In the ultrasound study of elderly men mentioned earlier, testicular volume was strongly linked to markers of testicular function like inhibin B and the ratio of testosterone to the brain hormone that stimulates its production.3The Journal of Clinical Endocrinology & Metabolism. Testicular Volume in Relation to Hormonal Indices of Gonadal Function in Community-Dwelling Elderly Men In practical terms, a smaller testicle in an older man is often both a cause and a consequence of lower hormone output.
Why It Might Feel Like They Are Getting Bigger
If the testicles themselves shrink with age, why do many men feel like things are getting larger down there? Several things conspire to create that impression, and some of them are genuinely worth paying attention to.
The most obvious one is scrotal sagging. The skin and connective tissue of the scrotum lose elasticity over the years, just like skin everywhere else on your body. The scrotum hangs lower and looks more voluminous even as the testicles inside it are slightly smaller than they used to be. This is a cosmetic change in the scrotal skin, not a change in the testicles themselves. It is completely normal and almost universal in older men.
A more clinically relevant cause is a hydrocele, which is a buildup of fluid in the thin sac that surrounds each testicle. The fluid sits between two layers of tissue and can make the scrotum swell gradually over months or years.7Research Journal of Pharmacology and Pharmacodynamics. A Comprehensive Review on Hydrocele Hydroceles are common in older men and are usually painless, which means they can grow quite large before anyone notices.8PubMed. Epidemiology of hydrocele and spermatocele; incidence, treatment and complications A spermatocele, which is a fluid-filled cyst near the top of the testicle, can produce a similar lump or fullness. Neither of these represents the testicle itself growing; they are separate structures filling with fluid next to the testicle.
Infections can also cause the scrotum to swell suddenly. Epididymo-orchitis, an inflammation of the testicle and its neighboring tube, causes pain and swelling that can be dramatic.9PubMed Central. Outcome of acute epididymo-orchitis: risk factors for testicular loss Unlike the slow changes of aging, this kind of swelling comes on over days and is usually accompanied by pain, redness, or fever. It needs medical attention promptly.
When Swelling Might Be Serious
Testicular cancer is overwhelmingly a young man’s disease, with most cases hitting between the late teens and mid-30s. But the types of testicular tumors that appear change with age. In men over 50 and especially over 70, the most common testicular malignancy is lymphoma rather than the germ-cell tumors that affect younger men.10PubMed Central. Testicular cancer among US men aged 50 years and older So while testicular cancer overall becomes rarer as you age, an unexplained lump or firmness in the testicle of an older man should not be dismissed. The incidence of certain subtypes, including sex cord stromal tumors and testicular lymphoma, actually increases steadily with age.
The practical lesson here is straightforward: any new, painless lump or one-sided swelling that persists for a few weeks deserves an ultrasound, regardless of your age. The conditions that cause scrotal swelling in older men are overwhelmingly benign, but a quick imaging exam rules out the rare exceptions.
Varicoceles and the Aging Vascular System
A varicocele is an enlargement of the veins inside the scrotum, similar to a varicose vein in the leg. They are common at all ages but tend to become more noticeable as blood-vessel walls lose tone over the decades. In elderly men, varicoceles (especially when present on both sides) are associated with smaller and softer testicles.11PubMed. Prevalence and effect of varicoceles in an elderly population The veins themselves can give the scrotum a fuller, heavier feel, which some men might interpret as the testicles getting bigger. In reality, the opposite is happening: the varicocele is impairing the testicle and contributing to its gradual atrophy. Interestingly, the same study found that varicoceles in older men did not directly lower blood testosterone levels, even though they affected the testicles physically.
Obesity, Metabolic Health, and Testicular Volume
Body weight has its own independent effect on testicular size, and this muddies the aging picture because men tend to gain weight as they get older. Research in obese men found that testicular volume dropped by roughly 0.4 milliliters for each one-point increase in body mass index, independent of age and testosterone levels.12PubMed Central. Testicular volume and clinical correlates of hypothalamic-pituitary-testicular function: A cross-sectional study in obese men That might sound small per BMI point, but across a span of 10 or 15 BMI units, the effect adds up. Higher levels of luteinizing hormone (the brain’s “make more testosterone” signal) were also independently tied to smaller testicles in the same analysis, suggesting that in obese men the testicles are both receiving stronger hormonal demands and responding less effectively.
The practical implication is that some of the testicular shrinkage men attribute to aging may actually be driven by weight gain, metabolic health, or both. In other words, maintaining a healthier weight might slow down part of the decline, though separating the effects of weight and age cleanly is difficult in any individual person.
Medications That Can Shrink the Testicles
Two categories of medication deserve attention here because they are common among aging men and can cause testicular changes that get blamed on getting older.
Testosterone replacement therapy is the big one. When you take testosterone from an outside source, the brain detects the higher blood levels and dials down its signals to the testicles. Without that stimulation, the testicles shrink. A study tracking men on testosterone replacement found that average testicular volume dropped from about 16.5 milliliters before treatment to about 13.7 milliliters after two years, with the shrinkage becoming significant by six months. Men who started with larger testicles and those using injectable testosterone rather than topical formulations were more likely to experience noticeable atrophy.13The Journal of Sexual Medicine. Characteristics of testicular atrophy during testosterone replacement therapy (TRT) This is one of the more ironic trade-offs in men’s health: treating low testosterone can make the testicles even smaller.
Finasteride, widely prescribed for hair loss and enlarged prostate, is the other drug that shows up in the research. Animal studies have shown that finasteride can reduce testicular weight and damage the structure of sperm-producing tissue, with effects including thinning of the lining inside the seminiferous tubules and damage to the cells that support sperm development.14Reproductive Toxicology. Protective role of hesperidin in finasteride-induced testicular toxicity in adult male Wistar rats: Insights into oxidative stress, apoptosis, and ultrastructure of seminiferous tubules Longer-term exposure in animal models confirmed that the structural damage persisted even after several months.15Toxicology. Long-term oral exposure to finasteride and different doses of minoxidil induces testicular and epididymal alterations in adult Balb/c mice Whether these animal findings translate directly to humans at standard doses is still debated, but men on finasteride who notice testicular changes should be aware that the drug is a plausible contributor.
Other Risk Factors for Reduced Testicular Size
Age is far from the only thing that affects testicular size. That same large study that isolated the effects of aging found that malnutrition, heavy alcohol use, cancer, and serious chronic illness were all independent risk factors for smaller testicles.5PubMed. Testicular size: the effects of aging, malnutrition, and illness On the other hand, diabetes, recreational drug use, and pelvic injuries were not associated with reduced testicular volume in the same data. This is a useful reminder that many of the factors that shrink the testicles are things that also get more common with age. A 65-year-old man who has been a heavy drinker for decades, has dealt with cancer, and is now underweight may have significantly smaller testicles than a healthy 65-year-old, and most of that difference is disease-driven rather than age-driven.
The difficulty for individuals is pulling apart these overlapping causes. You cannot easily tell whether a smaller or softer testicle is caused by aging, weight gain, a varicocele, alcohol, medication, or some combination. A doctor with an ultrasound and a blood panel can usually sort it out, though.
Why Testicular Size Varies So Much Between Species
If you have ever wondered why human testicles are the size they are in the first place, the answer is surprisingly tied to mating behavior. Across primates, species in which females routinely mate with multiple males have evolved larger testicles relative to their body weight, because producing more sperm gives each male a competitive advantage inside the reproductive tract. Species with single-male mating systems have relatively smaller testicles.16Nature. Testis weight, body weight and breeding system in primates17Journal of Human Evolution. Ejaculate quality, testes size and sperm competition in primates Humans fall somewhere in the middle of the primate range, which researchers have interpreted as evidence that our ancestors practiced a mix of mating strategies. This evolutionary context has nothing to do with aging, but it explains why human testicles landed at the size they did and why there is no biological “ideal” to compare yourself against.
Telling Normal Aging Apart from a Problem
Given everything above, a reasonable question is: when should you actually worry? Gradual, symmetrical changes over many years are almost certainly just aging doing its thing. The situations that warrant a visit to a doctor are more specific:
- Sudden swelling: one testicle rapidly becoming larger or tender over days, especially with fever, suggests infection or torsion and needs urgent evaluation.
- Painless hard lump: a firm mass that was not there before, even if it does not hurt, should be imaged to rule out a tumor.
- Pronounced asymmetry: one side getting noticeably larger than the other over weeks to months could indicate a hydrocele, spermatocele, or less commonly a growth.
- Heavy, dragging sensation: a feeling of weight in the scrotum, especially when standing, may point to a varicocele that has become more significant.
None of these symptoms mean something is necessarily wrong, but all of them are easy to investigate with a physical exam and an ultrasound. The scrotum is one of those areas where people tend to delay seeking help out of embarrassment, and then spend months anxiously wondering whether something is normal. A five-minute exam usually resolves the question.
Can You Do Anything to Slow Testicular Aging
There is no exercise routine for your testicles, no supplement with strong evidence of preserving testicular volume, and no lifestyle hack that stops the biological clock inside the seminiferous tubules. But the research does point to a few factors that are within your control. Maintaining a healthy weight matters, given the independent link between obesity and smaller testicles. Limiting alcohol intake matters, since heavy drinking is one of the clearest non-age risk factors for testicular atrophy. Staying on top of infections, particularly sexually transmitted ones that can cause epididymo-orchitis, protects against inflammatory damage. And if you are on testosterone replacement therapy, understanding that some testicular shrinkage is a predictable side effect lets you weigh that cost against the benefits with your doctor rather than being blindsided by it.
The cellular and vascular changes that come with aging are, for now, not reversible. Researchers have begun investigating strategies targeting oxidative stress and cellular senescence within the testicle, but these are early-stage ideas, not treatments you can access today.6PubMed Central. Testicular ageing as a central hallmark of male senescence: characteristics, molecular mechanisms and emerging therapeutic strategies For the foreseeable future, testicular aging is something to understand and monitor rather than something to treat, unless it crosses into territory that affects fertility, hormone levels, or comfort.