What could be causing testicular atrophy with normal ultrasound scan, no varicocele, and normal testosterone levels?

Testicular Atrophy with Normal Imaging and Hormones

Despite normal ultrasound, absent varicocele, and normal testosterone levels, you should measure FSH and LH levels immediately, as elevated FSH (>7.6 IU/L) indicates primary testicular failure and spermatogenic dysfunction even when testosterone remains compensated. 1

Hormonal Evaluation is Critical

The normal testosterone level is misleading in this scenario. Measure serum FSH and LH to distinguish between primary testicular dysfunction and secondary causes. 2

• Elevated FSH (>7.6 IU/L) with normal/low LH and normal testosterone indicates primary testicular failure with compensated Leydig cell function—the testes are failing at sperm production but still producing adequate testosterone 1
• Low or low-normal LH with low-normal testosterone suggests secondary hypogonadism from pituitary dysfunction, requiring prolactin measurement 2
• The combination of testicular atrophy with elevated FSH strongly predicts spermatogenic failure, even when testosterone appears normal 1

Confirm True Atrophy with Proper Measurement

Normal ultrasound findings may reflect measurement error rather than truly normal testes. Testicular volumes below 12 mL are definitively atrophic and associated with impaired spermatogenesis. 1, 3

• Request repeat scrotal ultrasound with explicit attention to proper measurement technique using the Lambert formula: Length × Width × Height × 0.71 3
• Physical examination with Prader orchidometer provides reliable volume assessment and is more cost-effective than ultrasound for routine measurement 3
• Size discrepancy between testes >2 mL or 20% warrants further evaluation to exclude pathology, regardless of absolute volume 3

Consider Genetic Causes

With confirmed bilateral testicular atrophy and abnormal hormonal findings, genetic evaluation becomes essential:

• Klinefelter syndrome (47,XXY) is the most common chromosomal abnormality causing testicular atrophy and presents with small firm testes, elevated FSH, and variable testosterone levels 1
• Karyotype testing is strongly recommended for males with severe oligospermia or non-obstructive azoospermia, as chromosomal abnormalities occur in 10% of these patients 1, 4
• Y-chromosome microdeletion testing should be performed if sperm concentration is <1 million/mL or azoospermia is present 2, 4

Evaluate for Subclinical Conditions

Several conditions cause testicular atrophy despite normal initial workup:

• History of cryptorchidism (even if corrected) causes persistent testicular dysfunction and atrophy 3
• Chronic medication use: opioids, corticosteroids, or anabolic steroids suppress the hypothalamic-pituitary-gonadal axis 2
• Systemic diseases: HIV/AIDS, diabetes, prior chemotherapy, or testicular radiation cause progressive testicular damage 2
• Subclinical varicocele may be present but is irrelevant—only palpable varicoceles benefit from treatment, and ultrasound should not be used to hunt for non-palpable varicoceles 2, 4

Cancer Surveillance is Mandatory

Testicular atrophy (<12 mL) significantly increases testicular cancer risk and requires ongoing monitoring. 1, 3

• Men with testicular atrophy should perform monthly testicular self-examination for early detection of masses 1
• In men under 30 years with testicular volume <12 mL and history of cryptorchidism, there is a >34% risk of intratubular germ cell neoplasia, which progresses to invasive cancer in 70% within 7 years if untreated 3
• Testicular biopsy should be considered for men with atrophic testes (<12 mL) and testicular microcalcification on ultrasound 1

Fertility Assessment

Even without fertility concerns currently, document baseline reproductive potential:

• Semen analysis is essential to assess the functional impact of testicular atrophy on sperm production 1, 4
• The assessment of combined ejaculate parameters (concentration, motility, morphology, total count) is more predictive of testicular function than any single parameter 1
• If azoospermia or severe oligospermia is present, microsurgical testicular sperm extraction (micro-TESE) may retrieve sperm from focal areas of preserved spermatogenesis, with 1.5 times higher success than conventional extraction 1

Common Pitfalls to Avoid

• Do not assume normal testosterone excludes testicular pathology—FSH elevation indicates primary testicular failure even when testosterone is maintained through compensatory mechanisms 1
• Do not rely solely on ultrasound reporting "normal" findings—request specific testicular volume measurements and compare to the 12 mL threshold 3
• Do not treat subclinical varicoceles found on ultrasound—only palpable varicoceles improve fertility outcomes after repair 2, 4
• Do not delay genetic counseling if abnormalities are detected, as genetic defects may transmit to offspring through assisted reproduction 4