Is a testicle size of 12 milliliters (ml) normal in an adult male?

Is a 12 mL Testicle Normal in an Adult Male?

A testicular volume of 12 mL in an adult male is below normal and meets the threshold for testicular atrophy, which warrants clinical evaluation for potential fertility issues and increased cancer risk. 1

Normal Testicular Volume Reference Values

• The normal adult testicular volume is approximately 18 mL based on population studies of healthy young men. 2
• In a large study of 1,139 normal young adults aged 19-27 years, the mean testicular volume was 18.37 mL (left) and 18.13 mL (right), with the lower cutoff for normal being around 18 mL. 2
• Infertile men have significantly smaller testicular volumes (median 15 mL) compared to fertile controls (median 22.5 mL). 3

Clinical Significance of 12 mL Testicular Volume

At 12 mL, this testicular volume is classified as atrophic according to European Association of Urology guidelines, which define atrophic testes as <12 mL. 1, 4

Impact on Fertility

• Testicular volumes below 15 mL are strongly associated with oligoasthenoteratozoospermia (OAT), while volumes below 12 mL have good predictive ability for detecting non-obstructive azoospermia. 3
• Testicular volume positively correlates with sperm density, total sperm count, total motile sperm count, and testosterone levels. 5, 2
• Mean sperm density falls into the oligozoospermic range when testicular volume is below 10 mL, with testicular length below 3.5 cm, depth below 1.75 cm, or width below 2.5 cm. 5

Hormonal Implications

• Testicular volume is negatively correlated with FSH and LH levels, and positively correlated with testosterone. 2
• When testicular atrophy is accompanied by elevated FSH levels above 7.6 IU/L, this strongly indicates spermatogenic failure. 4

Required Clinical Evaluation

Men with testicular volumes of 12 mL require comprehensive assessment due to both fertility concerns and increased cancer risk. 1, 4

Physical Examination Priorities

• Assess both testes for size asymmetry, consistency, and presence of varicoceles or epididymal abnormalities. 4
• Palpate for presence of vas deferens bilaterally to rule out congenital bilateral absence. 6
• Perform digital rectal examination to assess prostate and seminal vesicle pathology. 6

Essential Laboratory Testing

• Obtain at least two semen analyses performed at least one month apart to assess sperm concentration, motility, and morphology. 1, 7
• Measure serum FSH and testosterone levels—elevated FSH (>7.6 IU/L) with atrophic testes strongly suggests spermatogenic failure. 4, 6
• If sperm concentration is <5-10 million/mL or azoospermia is present, karyotype testing and Y-chromosome microdeletion analysis are mandatory before proceeding with assisted reproduction. 4, 6

Imaging Considerations

• Scrotal ultrasound provides accurate testicular volume assessment and is indicated when physical examination is difficult or when testicular mass is suspected. 1, 4
• Ultrasound measurements are the gold standard for testicular volume quantitation, as clinical methods (orchidometers, calipers) overestimate volumes by 70-250%. 8

Cancer Surveillance Requirements

Atrophic testes (<12 mL) are a recognized risk factor for testicular germ cell tumors and require ongoing monitoring. 1, 4

• Men with atrophic testes should be taught testicular self-examination for early detection of testicular cancer. 4
• If testicular microcalcification is present on ultrasound in addition to atrophic testes, testicular biopsy should be offered due to significantly increased cancer risk. 1, 4
• Long-term monitoring of both testes is necessary, as the contralateral testicle may also be affected even in unilateral conditions. 4

Common Clinical Pitfalls

• Do not rely on orchidometer measurements alone, as they grossly overestimate ultrasound volumes by including scrotal skin and epididymis. 8
• Do not perform single semen analysis—at least two samples one month apart are required due to significant intra-individual variation. 1, 7
• Do not delay genetic testing (karyotype and Y-chromosome analysis) if severe oligospermia or azoospermia is present, as results impact counseling and treatment decisions before assisted reproduction. 6
• Do not treat subclinical (non-palpable) varicoceles—only palpable varicoceles with abnormal semen parameters warrant treatment. 1, 6