Do men with testicular atrophy still maintain some sperm production and at what testicular volume does azoospermia (absence of sperm in the ejaculate) typically develop?

Testicular Atrophy and Sperm Production

Direct Answer

Most men with small, atrophied testicles do maintain some sperm production, and there is no absolute testicular volume cutoff below which azoospermia invariably develops. Even men with severe testicular atrophy (volumes ≤2 mL) have a 55% sperm retrieval rate with microsurgical testicular sperm extraction (micro-TESE), identical to men with normal-sized testes 1.

Understanding the Volume-Fertility Relationship

Critical Volume Thresholds

• Testicular volumes <12 mL are definitively considered atrophic and associated with impaired spermatogenesis, but this does NOT mean complete absence of sperm 2, 3
• Mean testicular volume strongly correlates with total sperm count and sperm concentration, but this is a statistical correlation, not an absolute predictor 3
• Even volumes of 2 mL or less (severe atrophy) yield successful sperm retrieval in 55% of cases with micro-TESE, demonstrating that focal areas of spermatogenesis persist despite severe atrophy 1

The FSH-Atrophy-Azoospermia Connection

• FSH levels >7.6 IU/L indicate impaired but not necessarily absent spermatogenesis, with non-obstructive azoospermia typically presenting with low testicular volume, normal semen volume, and elevated FSH 2
• Up to 50% of men with non-obstructive azoospermia and elevated FSH still have retrievable sperm despite the hormonal and anatomical indicators of testicular failure 2
• Men with markedly elevated FSH (≥3 times normal) and testicular atrophy demonstrate mature sperm on testicular biopsy in 30% of cases, most commonly showing severe hypospermatogenesis rather than complete Sertoli-cell-only pattern 4

Clinical Patterns by Testicular Volume

Volumes 10-12 mL (Borderline Atrophic)

• Typically associated with oligospermia rather than azoospermia, with FSH levels >7.6 IU/L indicating impaired but not absent spermatogenesis 3
• Bilateral hypotrophy (<14 mL) in men with varicoceles increases the risk of total motile sperm count <20 million by nearly 9-fold compared to men without hypotrophy 5

Volumes 2-10 mL (Moderate to Severe Atrophy)

• Sperm retrieval rate of 56% with micro-TESE, with clinical pregnancy rates of 50% and live birth rates of 43% when sperm are successfully retrieved 1
• Biofunctional sperm parameters (mitochondrial membrane potential, DNA fragmentation, chromatin compactness) worsen linearly with decreasing testicular volume, but sperm remain present 6

Volumes ≤2 mL (Severe Atrophy)

• Sperm retrieval rate of 55% with micro-TESE, identical to larger volumes, demonstrating that severe atrophy does not preclude sperm production 1
• Younger men (<30 years) with Klinefelter syndrome and severe atrophy have an 81.8% sperm retrieval rate, significantly higher than older men without Klinefelter syndrome (33%) 1
• 72.6% of men with volumes ≤2 mL have Klinefelter syndrome, compared to only 5.3% of men with volumes >2 mL 1

Why Azoospermia Doesn't Have a Volume Cutoff

Focal Spermatogenesis Persists

Micro-TESE succeeds precisely because it identifies focal areas of sperm production within otherwise atrophic testes, explaining why testicular volume alone cannot predict sperm presence 2, 1. The technique is 1.5 times more successful than conventional TESE because it can locate these microscopic islands of spermatogenesis 2.

Genetic Factors Trump Volume

• Complete AZFa and AZFb Y-chromosome microdeletions predict near-zero sperm retrieval success, but these genetic factors—not testicular volume—determine the outcome 2, 3
• AZFc deletions are associated with variable presentations including oligospermia or azoospermia, with successful sperm retrieval via TESE in 53-75% of cases regardless of testicular size 3

Histological Patterns Matter More

• Men with maturation arrest can have normal FSH and testicular volume despite severe spermatogenic dysfunction, while others with severe atrophy maintain hypospermatogenesis 2
• The most common finding in men with elevated FSH and atrophy who have retrievable sperm is severe hypospermatogenesis, not complete absence of germ cells 4

Critical Clinical Caveats

Sperm Pelleting Reveals Hidden Sperm

Semen centrifugation (sperm pelleting) identifies motile or nonmotile sperm in 22.8% of men with non-obstructive azoospermia who were considered to have complete absence of sperm on routine semen analysis 7. This technique should be performed in all men with apparent azoospermia before concluding that no sperm are present 7.

Age Is the Only Consistent Predictor

On multivariable analysis, younger age is the only preoperative factor associated with successful sperm retrieval in men with small testes (≤2 mL), with no cutoff point beyond which sperm cannot be retrieved 1. This emphasizes that chronological testicular aging matters more than absolute volume.

Bilateral vs. Unilateral Atrophy

Bilateral testicular hypotrophy predicts severe impairment of semen quality, while unilateral hypotrophy alone does not predict low total motile sperm count 5. This suggests that compensatory mechanisms from one normal testis can maintain adequate sperm production.

Practical Algorithm for Assessment

1. Confirm true azoospermia with sperm pelleting (centrifugation of semen) rather than relying on routine semen analysis alone 7
2. Measure testicular volume using Prader orchidometer (good surrogate for ultrasound, easier and more cost-effective) 3
3. Obtain FSH, LH, and testosterone levels to distinguish primary testicular failure from secondary hypogonadism 2
4. Perform karyotype and Y-chromosome microdeletion testing if sperm concentration is <1 million/mL or confirmed azoospermia 2, 3
5. Counsel that micro-TESE offers 40-60% sperm retrieval rates even with severe atrophy and elevated FSH, with younger age predicting better outcomes 2, 1