My testicles appear smaller though my semen analysis and serum testosterone are normal; what evaluation should I pursue?

Testicular Size Assessment with Normal Hormones

Your normal testosterone and semen analysis strongly suggest that any perceived testicular shrinkage is either measurement error, normal anatomical variation, or clinically insignificant—but you should confirm testicular volume with proper measurement and rule out high-risk scenarios before reassurance.

Why Normal Labs Are Reassuring

• Testicular volume strongly correlates with sperm production: Mean testicular size has the strongest correlation with total sperm count and sperm concentration, meaning normal semen parameters argue against significant testicular atrophy. 1

• Normal testosterone indicates adequate Leydig cell function: If your testosterone is truly normal, your testes are producing adequate hormones, which would be impaired with significant atrophy. 2

• The 12 mL threshold defines pathological atrophy: Testicular volumes below 12 mL are definitively considered atrophic when associated with impaired spermatogenesis, elevated FSH, or history of cryptorchidism—none of which you have. 3

Essential Next Steps to Confirm Your Status

Obtain Accurate Testicular Volume Measurement

• Physical examination with Prader orchidometer is the most practical first step, providing a good surrogate for ultrasound volume measurement and being more cost-effective. 3

• Scrotal ultrasound with proper technique should be performed if orchidometer measurement suggests volume <12 mL or if there is >2 mL (or >20%) size discrepancy between testes. 3

• Use the Lambert formula (Length × Width × Height × 0.71) for accurate volume calculation, as the traditional ellipsoid formula (0.52 coefficient) systematically underestimates volume by 20-30% and may lead to inappropriate classification of atrophy. 3

Rule Out High-Risk Scenarios That Mandate Further Workup

Even with normal labs, certain clinical contexts require additional evaluation:

• History of cryptorchidism (undescended testicles) dramatically increases risk of testicular atrophy and cancer, with men having 3.6-7.4 times higher risk of germ cell tumors. 3

• Age under 30-40 years with volume <12 mL carries ≥34% risk of intratubular germ cell neoplasia if testicular cancer develops, and 70% of untreated cases progress to invasive cancer within 7 years. 3

• Rapid testicular atrophy or palpable mass warrants urgent urology referral regardless of hormone levels. 3

Hormonal Evaluation to Complete the Picture

Measure FSH to Assess Testicular Reserve

• FSH >7.6 IU/L indicates reduced testicular reserve and impaired spermatogenic capacity, even when current sperm production appears normal. 3, 4

• Morning serum FSH, LH, and total testosterone should be drawn between 08:00-10:00 h on at least two separate occasions to obtain reliable baseline values. 3

• Elevated FSH with normal testosterone and sperm count represents compensated testicular dysfunction—your pituitary is working harder to maintain normal output, suggesting reduced reserve. 3

Interpret the FSH-Testosterone-Sperm Pattern

• Normal FSH (<7.6 IU/L) with normal testosterone and sperm essentially rules out significant testicular atrophy and confirms your perception is likely inaccurate. 3, 4

• Mildly elevated FSH (7.6-12 IU/L) with normal labs indicates borderline testicular reserve requiring monitoring every 6-12 months but no immediate intervention. 3, 5

• FSH >12 IU/L despite normal current function warrants genetic testing (karyotype and Y-chromosome microdeletion) and consideration of sperm banking. 3, 5

Common Pitfalls and How to Avoid Them

Measurement Error Is Extremely Common

• Incorrect caliper placement during ultrasound can lead to severely atrophic and inconsistent volume calculations—request repeat ultrasound with explicit attention to proper measurement technique if initial results suggest atrophy. 3

• High-frequency probes (>10 MHz) should be used to maximize resolution and accurate caliper placement. 3

• The same sonographer should perform serial measurements when possible, or measurements should be remeasured on previous scans by the current operator to minimize inter-scan variability. 3

True Biological Change Is Unlikely Without Symptoms

• True biological change in testicular size over 4 weeks is extremely unlikely in adults unless there is acute pathology like torsion, trauma, or infection. 3

• Gradual atrophy occurs over months to years in conditions like varicocele, hypogonadism, or post-chemotherapy—sudden perceived shrinkage is almost always measurement or perception error. 3

Never Start Testosterone If You Care About Fertility

• Exogenous testosterone completely suppresses spermatogenesis through negative feedback on the hypothalamus and pituitary, causing azoospermia that can take months to years to recover. 2, 3, 4

• This applies even if your current testosterone is normal—supplementation will shut down your own production and eliminate sperm. 3, 5

When to Worry vs. When to Be Reassured

You Can Be Reassured If:

• Testicular volume is ≥12 mL bilaterally with <2 mL difference between sides. 3

• FSH is <7.6 IU/L with normal testosterone and normal semen analysis. 3, 4

• No history of cryptorchidism, chemotherapy, radiation, or chronic steroid use. 3, 6

• No palpable masses, pain, or rapid change in size. 3

You Need Further Workup If:

• Confirmed volume <12 mL on proper measurement (orchidometer or ultrasound with Lambert formula). 3

• Size discrepancy >2 mL or >20% between testes warrants ultrasound to exclude pathology. 3

• History of cryptorchidism at any age, especially if corrected after age 2 years. 3, 6

• FSH >7.6 IU/L indicating reduced testicular reserve. 3, 4

• Age <30-40 years with any concern for atrophy given higher cancer risk. 3

Bottom Line Algorithm

1. Obtain accurate testicular volume measurement with Prader orchidometer or ultrasound using Lambert formula (0.71 coefficient). 3

2. If volume ≥12 mL bilaterally with <2 mL difference: Measure morning FSH, LH, and testosterone on two occasions—if FSH <7.6 IU/L, you are reassured and need no further workup. 3

3. If volume <12 mL or FSH >7.6 IU/L: Obtain complete hormonal panel, consider genetic testing if sperm concentration <5 million/mL, and discuss sperm banking if fertility is desired. 3, 5

4. If history of cryptorchidism or age <30 years with volume <12 mL: Refer to urology for consideration of testicular biopsy given ≥34% risk of intratubular germ cell neoplasia. 3

5. Avoid exogenous testosterone completely if current or future fertility is desired. 2, 3, 4