Which Ultrasound Measurement is More Likely Correct?
The 4cm × 4cm measurement is more likely correct given your normal FSH (9.9 IU/L) and normal sperm count (70 million/mL), as these parameters indicate preserved testicular function that correlates with normal testicular volume rather than atrophy. 1
Understanding the Clinical Context
Your hormone and sperm parameters tell a clear story:
FSH 9.9 IU/L is borderline-elevated but not severely abnormal. While FSH >7.6 IU/L suggests some degree of testicular dysfunction, this level does not indicate primary testicular failure, which typically presents with FSH levels much higher (often >15-20 IU/L). 1
Sperm count of 70 million/mL is well above the WHO lower reference limit of 16 million/mL, confirming active and quantitatively normal spermatogenesis. 1
The combination of mildly elevated FSH with normal sperm production represents "compensated hypospermatogenesis" - your pituitary is working slightly harder (elevated FSH) to maintain normal sperm output, but the testes are responding appropriately. 2
Why Testicular Size Matters
Men with non-obstructive azoospermia (complete testicular failure) typically present with testicular atrophy (volume <12 mL, length typically <3.5 cm), elevated FSH (usually >15 IU/L), and absent or severely reduced sperm counts. 1, 3 This does not match your clinical picture.
Testicular volume of 4cm length corresponds to approximately 12-15 mL volume, which is at the lower end of normal but not atrophic. 1 This size is consistent with maintained spermatogenesis, as evidenced by your normal sperm count.
The 3.1-3.4 cm measurement would suggest testicular atrophy and would typically correlate with:
- FSH levels significantly higher than yours (often >15-20 IU/L) 1
- Severe oligospermia (<5 million/mL) or azoospermia 1, 3
- Primary testicular failure 1
The FSH-Testicular Size-Sperm Count Relationship
FSH levels are negatively correlated with spermatogenesis - higher FSH indicates the pituitary is compensating for reduced testicular function. 1, 4 However, your FSH of 9.9 IU/L with a sperm count of 70 million/mL demonstrates that your testes are responding adequately to FSH stimulation, which requires preserved testicular volume and architecture.
Research shows that men with FSH >7.5 IU/L have a 5-13 fold higher risk of abnormal sperm concentration compared to men with FSH <2.8 IU/L, but this refers to oligospermia (reduced counts), not normal counts like yours. 5 Your normal sperm count despite borderline-elevated FSH indicates your testicular reserve is sufficient, which correlates with preserved testicular size.
Important Clinical Implications
You have "compensated hypospermatogenesis" - a condition where mildly elevated FSH maintains normal sperm production, but you are at higher risk for future decline in semen parameters. 2 Men with this pattern should:
- Undergo repeat semen analysis every 6-12 months to monitor for declining sperm counts 2
- Consider sperm cryopreservation (banking 2-3 ejaculates) if planning to delay fertility, as your testicular reserve may decline over time 1
- Avoid exogenous testosterone or anabolic steroids completely, as these will suppress FSH and cause azoospermia 1, 4
Common Pitfalls to Avoid
Ultrasound measurements can vary between operators and techniques. 1 The 3.1-3.4 cm measurement may represent technical error, measurement of a different testicular dimension, or compression during scanning.
Do not assume testicular atrophy based on a single ultrasound measurement that contradicts your hormonal and semen parameters. 1 The functional evidence (normal sperm count) outweighs a single discrepant imaging finding.
If there is persistent uncertainty, repeat scrotal ultrasound with volume calculation (length × width × height × 0.71) by an experienced sonographer, and correlate with physical examination by a reproductive urologist. 1, 3