Normal Testicular Size
Normal adult testicular volume ranges from approximately 12-25 ml, with mean values around 13-14 ml per testis, measured by ultrasound or orchidometer. 1, 2
Standard Reference Values
Adult Men
- Mean testicular volume: 13-14 ml per testis 2
- Normal range extends from 12-25 ml 1, 2
- Volumes below 12 ml are considered small or atrophic and warrant further investigation 3, 1
Clinical Significance of Size Thresholds
Testicular volumes less than 12 ml carry important clinical implications:
- Associated with >34% risk of intratubular germ cell neoplasia in contralateral testis 1
- Correlate with impaired spermatogenesis and reduced fertility potential 1, 4
- Indicate need for contralateral biopsy in testicular cancer patients, especially those under 30 years 3, 1
Developmental Progression in Boys
Testicular growth follows a predictable pattern through childhood and adolescence: 5, 6
- Neonatal testis: mean volume 0.35 ml 5
- Ages 0-8 years: volume approximately 1.2-1.3 ml 5
- Intensive growth begins at age 10 years, with 2.5-fold increase in length/width 5
- Age 13 years: all boys exceed 3 ml volume 6
- Ages 16.5-18 years: volume ranges 6-22 ml, approaching adult size 6
- By age 17: mean volume reaches 12.8 ml 5
Correlation with Testicular Function
Testicular size directly correlates with reproductive function: 4
- Strongest correlation with serum FSH levels, total sperm count, and sperm concentration 4
- Significant correlation with sperm motility, viability, and morphology 4
- Testes smaller than 14 ml show impaired sperm quantity and quality 4
- Mean testicular size is the most reliable physical parameter for rapidly assessing andrological status 4
Measurement Methods
The Prader orchidometer provides accurate, cost-effective measurement in clinical practice and serves as a good surrogate for ultrasound volume assessment 1. Ultrasound measurement using the ellipsoid formula (length × width × height × π/6) remains the gold standard for precise volumetric assessment 5, 6.
Important Measurement Considerations
- External caliper measurements overestimate dimensions compared to ultrasound: length by 5.7 mm, thickness by 2.9 mm, width by 1.4 mm 5
- Ultrasound is superior for detailed evaluation as it accounts for skin thickness, testicular coats, and epididymal position 5
- No statistically significant differences exist between right and left testicular volumes in healthy individuals 5
Clinical Context for Small Testes
Risk factors associated with reduced testicular volume include: 3, 1
- History of cryptorchidism (undescended testicles) 3, 1
- Age under 30 years with testicular cancer 3
- Hypogonadism and unexplained infertility 2
However, slightly smaller testis with normal vascularity and homogeneous ultrasound architecture does not indicate permanent infertility and should be reassuring 7. Even men with unilateral cryptorchidism achieve paternity rates nearly equivalent to men without cryptorchidism, despite smaller affected testis size 7.