Are small testicles (testicular hypoplasia) a concern?

Small Testicles: When to Worry and When to Reassure

Small testicles are generally not a concern in most cases unless they are associated with specific risk factors including testicular volume <12 mL, history of cryptorchidism, infertility concerns, or other clinical red flags that warrant further evaluation. 1, 2, 3

Understanding What "Small" Actually Means

The critical threshold for clinical concern is **testicular volume <12 mL**, which is universally considered atrophic and pathologically significant. 1, 2, 3 Normal adult testicular length ranges from 3.5-5 cm, corresponding to volumes typically >12-14 mL. 3 Using a Prader orchidometer (the preferred clinical tool), volumes of 15-18 mL are associated with normal spermatogenesis and adequate fertility potential. 2

A common pitfall: The Prader orchidometer tends to overestimate volume compared to ultrasound, so a reading of 15 mL may actually correspond to 16-18 mL on ultrasound. 2 This is clinically acceptable—ultrasound should be reserved for specific indications, not routine screening. 3

When Small Testicles ARE a Concern

Small testicles warrant immediate evaluation in these scenarios:

High-Risk Situations Requiring Action:

• **Testicular volume <12 mL in men under 30-40 years:** These patients have a >34% risk of intratubular germ cell neoplasia (GCNIS) in the contralateral testis. 2, 3 This is particularly critical in patients with a history of testicular cancer or cryptorchidism. 1

• History of cryptorchidism (undescended testicles): Even after successful orchidopexy, these testes remain at significantly elevated risk for both malignancy and infertility. 4, 3, 5 The cryptorchid testis has an increased incidence of malignancy and markedly elevated rate of sterility. 5

• Infertility concerns with small testes: Mean testicular size strongly correlates with total sperm count and sperm concentration. 2, 6 Testicular atrophy with elevated FSH levels >7.6 IU/L strongly indicates spermatogenic failure. 1

• Testicular microcalcification on ultrasound: Men with atrophic testes (<12 mL) and testicular microcalcification should be offered testicular biopsy due to increased risk of testicular germ cell tumors. 1

Clinical Algorithm for Evaluation:

1. Measure testicular volume using Prader orchidometer at routine physical examination. 2, 3

2. If volume <12 mL, assess for:

   • History of cryptorchidism 4, 3
   • Infertility or fertility concerns 1, 2
   • Age <30-40 years (higher GCNIS risk) 2, 3
   • Size discrepancy >2 mL or 20% between testes 3

3. Order hormonal evaluation if concerning features present:

   • FSH, LH, testosterone 1, 6
   • FSH >7.6 IU/L with atrophy indicates spermatogenic failure 1

4. Consider genetic testing in severe cases:

   • Karyotype for severe oligospermia or non-obstructive azoospermia 1
   • Y-chromosome microdeletion testing 1
   • Klinefelter syndrome (47,XXY) is the most common chromosomal abnormality with testicular atrophy 1, 5

5. Ultrasound indications (not routine):

   • Large hydrocele obscuring examination 1, 2
   • Inguinal testis 2
   • Epididymal enlargement/fibrosis 1, 2
   • Thickened scrotal skin 2

When Small Testicles Are NOT a Concern

Normal prepubertal boys: Small testicles are completely normal in prepubertal boys, irrespective of height and weight. 5 This is a critical reassurance point for worried parents.

Absence of risk factors: If testicular volume is ≥12 mL, there is no history of cryptorchidism, no infertility concerns, and no palpable masses, routine monitoring at well-child visits is sufficient. 4

Important caveat: Even "normal-sized" testes cannot definitively predict fertility status—if infertility is a concern, semen analysis is required regardless of testicular size. 3

Long-Term Monitoring Recommendations

For men with confirmed testicular atrophy (<12 mL):

• Regular testicular self-examination for early detection of testicular cancer 1
• Monitor the contralateral testicle, which may also be affected even in unilateral conditions 1
• Consider microsurgical testicular sperm extraction (micro-TESE) for non-obstructive azoospermia—it is 1.5 times more successful than non-microsurgical extraction 1

Common Causes of Acquired Testicular Atrophy

Beyond congenital conditions, testicular atrophy can result from:

• Mumps orchitis or trauma (including torsion) 5
• Chronic diseases: liver cirrhosis, chronic alcoholism, hemochromatosis 5
• Medications: immunosuppressive and chemotherapy agents 5, 7
• Radiation exposure: particularly cranial and testicular irradiation 7
• Surgical complications: injury to blood vessels during orchidopexy 5

Critical pitfall to avoid: Do not hunt for subclinical varicoceles with ultrasound—only palpable varicoceles benefit from treatment, as non-palpable varicoceles do not improve semen parameters or fertility rates. 3