Is a testicle size of 3.8cm considered normal in an adult male?

Is a 3.8cm Testicle Normal?

A testicle measuring 3.8cm in length is at the lower end of normal for adult males, corresponding to a volume of approximately 12-15ml, which represents the borderline threshold between normal and atrophic testicular size. 1

Understanding Testicular Size Measurements

Normal Adult Testicular Dimensions

• Adult testicular volumes greater than 12ml are generally considered normal, with volumes below 12ml definitively classified as atrophic and associated with significant pathology including impaired spermatogenesis. 1

• A 4cm testicular length corresponds to a volume of approximately 15-18ml, which is within the normal range for adult males, while a 3.8cm length suggests a volume closer to 12-15ml. 1

• The lower limit of normal testicular volume is 12ml, with volumes between 12-15ml considered borderline-small and warranting clinical correlation. 1

Measurement Considerations

• Testicular volume is the most precise description of testicular size and should be calculated using the Lambert formula: Length × Width × Height × 0.71. 1, 2

• The Prader orchidometer provides a good surrogate for ultrasound volume measurement and is easier to perform and more cost-effective in clinical practice. 1

• High-frequency ultrasound probes (>10 MHz) should be used to maximize resolution and accurate caliper placement when precise measurement is needed. 1

Clinical Significance of Borderline Testicular Size

Fertility Implications

• Testicular volumes below 12ml strongly correlate with impaired spermatogenesis, reduced total sperm count, and decreased sperm concentration. 1

• Mean testicular size has the strongest correlation with serum FSH levels, total sperm count, and sperm concentration, making it a valuable predictor of testicular function. 3

• Sperm production is directly dependent on testicular size, with both sperm quantity and quality impaired in testes smaller than 14ml. 4, 3

Cancer Risk Considerations

• Testicular volumes less than 12ml are associated with a higher risk of intratubular germ cell neoplasia (TIN), particularly in men under 30-40 years of age. 1

• In men under 30 years with testicular volume <12ml, there is a >34% risk of TIN in the contralateral testis if testicular cancer is present, and if untreated, invasive testicular tumor develops in 70% of TIN-positive testes within 7 years. 1

• History of cryptorchidism (undescended testicles) substantially increases cancer risk and mandates closer surveillance in men with small testicular volumes. 1

Recommended Clinical Evaluation

Essential Diagnostic Steps

• Obtain at least two semen analyses separated by 2-3 months to assess sperm concentration, motility, and morphology, as single analyses can be misleading due to natural variability. 1

• Measure serum FSH, LH, and total testosterone on morning samples to distinguish primary testicular dysfunction from secondary hypogonadism. 5, 1

• FSH levels above 7.6 IU/L with testicular atrophy strongly suggest spermatogenic failure, though this does not necessarily mean complete absence of sperm production. 5, 6

When to Pursue Further Workup

• Consider scrotal ultrasound if there is a size discrepancy between testes greater than 2ml or 20% to exclude pathology. 1

• Karyotype testing is strongly recommended if semen analysis shows severe oligospermia (<5 million/ml) or azoospermia, as chromosomal abnormalities occur in 10% of these patients. 1, 6

• Y-chromosome microdeletion testing should be performed if sperm concentration is <1 million/ml, as complete AZFa and AZFb deletions predict near-zero sperm retrieval success. 1, 6

High-Risk Scenarios Requiring Urgent Evaluation

• Age under 30 years with testicular volume <12ml and history of cryptorchidism warrants urology referral and consideration of contralateral testicular biopsy due to increased cancer risk. 1

• Presence of testicular microcalcifications on ultrasound increases testicular cancer risk 18-fold and should prompt testicular biopsy. 5

• Rapid testicular atrophy or development of a palpable testicular mass requires urgent urology referral. 5

Critical Pitfalls to Avoid

• Never prescribe exogenous testosterone if fertility is desired, as it will completely suppress spermatogenesis through negative feedback, potentially causing azoospermia that can take months to years to recover. 1, 6

• Do not use the traditional ellipsoid formula (0.52 coefficient) for clinical decision-making, as it systematically underestimates volume by 20-30% and may lead to inappropriate classification of testicular atrophy. 1

• Teach testicular self-examination given the increased cancer risk associated with smaller testicular volumes. 5, 1

Protective Actions for Fertility Preservation

• Consider sperm cryopreservation if follow-up semen analysis shows declining sperm parameters, banking 2-3 separate ejaculates with 2-3 days abstinence between collections. 6

• Avoid gonadotoxic exposures including anabolic steroids, excessive heat exposure to the testes, and smoking, as these can further impair spermatogenesis. 6

• Maintain a healthy body weight (BMI <25), as obesity and metabolic syndrome impair male fertility. 6