What are the possible causes and recommended diagnostic evaluation for asymptomatic testicular atrophy in an adult male with normal semen analysis, normal total testosterone, normal luteinizing hormone and follicle‑stimulating hormone levels, and scrotal ultrasound showing bilateral 9 mL testes without lesions or epididymal inflammation?

Asymptomatic Bilateral Testicular Atrophy: Causes and Diagnostic Approach

Your Clinical Picture

Your testicular volume of 9 mL bilaterally is definitively atrophic and warrants systematic evaluation, even though your current sperm count and hormones appear reassuring. 1

Your laboratory values show:

• Sperm concentration 60 million/mL = normal (well above the 15 million/mL threshold)
• Testosterone 40 nmol/L (≈1154 ng/dL) = high-normal to elevated
• LH 7.2 IU/L = upper-normal range
• FSH 9.9 IU/L = upper-normal, approaching the 12.4 threshold

The combination of bilateral 9 mL testes with FSH at 9.9 IU/L indicates reduced testicular reserve, meaning your testes are working harder (elevated FSH) to maintain currently adequate sperm production, but have limited capacity to compensate if additional stressors occur. 1

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Critical Context: The 12 mL Threshold

Testicular volumes below 12 mL are classified as atrophic and associated with impaired spermatogenesis, increased risk of intratubular germ cell neoplasia (TIN), and potential infertility. 1 At 9 mL bilaterally, you fall well below this threshold. 1

Cancer Risk Stratification

• If you are under 30–40 years old with volume <12 mL, you carry a ≥34% risk of TIN in the contralateral testis if testicular cancer develops. 1
• If TIN is left untreated, approximately 70% progress to invasive testicular cancer within 7 years. 1
• History of cryptorchidism (undescended testes) combined with volume <12 mL markedly increases malignancy risk and mandates intensified surveillance. 1

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Differential Diagnosis: Causes of Bilateral Testicular Atrophy

Primary Testicular Dysfunction (Hypergonadotropic Hypogonadism)

Genetic/Congenital:

• Klinefelter syndrome (47,XXY) is the most common genetic cause of primary testicular failure and should be considered when testicular volume is <12 mL with elevated FSH. 1
• History of bilateral cryptorchidism, especially when uncorrected or surgically corrected after puberty, markedly increases the risk of testicular atrophy. 1
• Myotonic dystrophy (type I and II) can present with painless bilateral testicular atrophy due to primary gonadal failure. 1

Acquired:

• Prior chemotherapy or pelvic/testicular radiation is a recognized cause of irreversible testicular shrinkage. 1, 2
• Autoimmune orchitis may affect both testes and produce a relatively painless atrophic process. 1
• Sickle-cell disease with recurrent vaso-occlusive crises can lead to chronic testicular hypoperfusion and atrophy. 1

Secondary Testicular Dysfunction (Hypogonadotropic Hypogonadism)

Exogenous Suppression:

• Chronic opioid use suppresses GnRH secretion, resulting in low gonadotropins and bilateral testicular atrophy. 1
• Anabolic-steroid or exogenous testosterone use causes complete suppression of spermatogenesis and can produce persistent atrophy for months to years after cessation. 1

Pituitary/Hypothalamic:

• Hyperprolactinemia from pituitary adenoma or prolactin-raising medications leads to secondary hypogonadism and testicular shrinkage. 1
• Kallmann syndrome or idiopathic hypogonadotropic hypogonadism present with low LH/FSH and small testes. 1

Systemic Conditions

• Type 2 diabetes mellitus/metabolic syndrome is linked to functional hypogonadism and reduced testicular volume. 1
• Chronic liver disease (cirrhosis) contributes to secondary hypogonadism and testicular atrophy. 1
• Chronic kidney disease is associated with decreased testosterone production and testicular size. 1
• HIV infection can cause both primary and secondary gonadal dysfunction leading to atrophy. 1

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Recommended Diagnostic Workup

Step 1: Repeat and Expand Hormonal Evaluation

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. 1

• Your FSH of 9.9 IU/L is at the upper limit of normal; values >7.6 IU/L in the context of testicular atrophy indicate reduced testicular reserve and impaired spermatogenic capacity. 1, 3
• Your LH of 7.2 IU/L is also upper-normal; elevated LH suggests primary testicular failure, whereas low or normal LH with low testosterone points toward secondary (hypothalamic-pituitary) dysfunction. 1
• When total testosterone is low, free testosterone should be measured by equilibrium dialysis together with sex-hormone-binding globulin (SHBG) to differentiate true hypogonadism from alterations in binding proteins. 1

Additional hormonal tests:

• Serum prolactin to exclude hyperprolactinemia as a cause of secondary hypogonadism. 1
• Iron saturation if hemochromatosis is suspected (can cause hypogonadotropic hypogonadism). 4

Step 2: Genetic Testing

Karyotype analysis is strongly recommended when FSH is elevated and testicular volume is <12 mL to screen for Klinefelter syndrome. 1

• Klinefelter syndrome (47,XXY) is the most common chromosomal abnormality associated with testicular atrophy and spermatogenic failure. 5
• Y-chromosome microdeletion testing should be offered if sperm concentration drops below 5 million/mL or azoospermia develops. 1, 3

Step 3: Imaging Confirmation

Request repeat scrotal ultrasound with explicit attention to proper measurement technique using the Lambert formula (Length × Width × Height × 0.71) to confirm testicular volume. 1

• Technical error in caliper placement during ultrasound may lead to incorrect testicular measurements, which can result in severely atrophic and inconsistent volume calculations. 1
• High-frequency probes (>10 MHz) should be used to maximize resolution and accurate caliper placement. 1
• Size discrepancy between testes >2 mL or 20% warrants further evaluation to exclude pathology, regardless of absolute volume. 1
• Assess for testicular microcalcifications, which increase testicular cancer risk 18-fold in infertile men. 5

Step 4: Detailed History

Obtain detailed history focusing on:

• Cryptorchidism (undescended testes) – dramatically raises the risk of atrophy and testicular cancer. 1
• Use of anabolic steroids, testosterone, opioids, or glucocorticoids – potential etiologic factors. 1
• History of chemotherapy or radiation to the pelvis/testes. 1
• Family history of Klinefelter syndrome or other hypogonadal disorders. 1
• Presence of systemic disease (diabetes, liver disease, chronic infection). 1

Step 5: Semen Analysis Monitoring

Repeat semen analysis every 6–12 months to detect early decline in sperm parameters, as single analyses can be misleading due to natural variability. 1

• Your current sperm concentration of 60 million/mL is reassuring, but testicular volume <12 mL strongly correlates with impaired spermatogenesis, lower total sperm count, and reduced sperm concentration. 1
• If sperm concentration drops below 20 million/mL, remeasure FSH, LH, and testosterone. 1

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Critical Management Considerations

Fertility Preservation

Discuss sperm banking before any surgical intervention or initiation of testosterone therapy. 1

• Never start testosterone replacement without first clarifying your fertility intentions, because exogenous testosterone suppresses the hypothalamic-pituitary-gonadal axis and can cause complete azoospermia that may take months to years to recover. 1

Cancer Surveillance

Teach testicular self-examination given increased cancer risk with smaller volumes. 1

• If you are under 30 years old with history of cryptorchidism, refer for testicular biopsy due to ≥34% risk of TIN. 1
• Urgent urology referral is indicated if: palpable testicular mass develops, rapid testicular atrophy occurs, or severe oligospermia (<5 million/mL) develops. 1

Factors That Could Accelerate Decline

• Exogenous testosterone or anabolic steroids will completely suppress spermatogenesis through negative feedback, causing azoospermia that can take months to years to recover. 1
• Chemotherapy or radiotherapy can cause additional impairment of semen quality for up to 2 years following treatment. 1

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Most Likely Explanation in Your Case

Given your upper-normal FSH (9.9 IU/L), upper-normal LH (7.2 IU/L), high-normal testosterone, and preserved sperm count, the most likely scenario is compensated primary testicular dysfunction – your hypothalamic-pituitary axis is working harder (elevated gonadotropins) to maintain adequate testosterone and sperm production despite reduced testicular mass. 6, 7

The key question is why your testes are atrophic. The most common reversible cause in young men is prior or ongoing anabolic steroid/testosterone use. 1 If this is excluded, genetic testing (karyotype) is the next priority to rule out Klinefelter syndrome. 1