In a male patient with elevated follicle‑stimulating hormone (FSH) and luteinizing hormone (LH) but normal serum testosterone, what is the most likely cause and recommended diagnostic work‑up?

Elevated FSH and LH with Normal Testosterone: Primary Testicular Dysfunction with Compensation

In a male patient with elevated FSH and LH but normal testosterone, the most likely diagnosis is compensated primary hypogonadism (hypergonadotropic hypogonadism), indicating underlying testicular dysfunction where the testes maintain adequate testosterone production only through increased gonadotropin stimulation. 1

Understanding the Pathophysiology

This hormonal pattern represents primary testicular failure with compensation rather than normal testicular function. The elevated gonadotropins (FSH and LH) signal that the hypothalamic-pituitary axis is working overtime to maintain what appears to be "normal" testosterone levels 1. The EAU 2025 guidelines explicitly recognize this as a distinct entity: "a compensated form can be characterised by normal testosterone levels and elevated production of luteinising hormones" 1.

Key Mechanistic Points:

• The normal testosterone is maintained at the expense of chronically elevated gonadotropins 2
• This represents impaired gonadal-pituitary feedback control 3
• FSH elevation specifically indicates seminiferous tubular dysfunction and impaired spermatogenesis 4, 5
• The pattern suggests the testes require supraphysiologic gonadotropin stimulation to produce normal-range testosterone

Most Likely Causes

Common Etiologies to Consider:

Primary testicular damage:

• Prior orchitis (mumps, viral) 2
• Varicocele
• Cryptorchidism history 1
• Testicular trauma
• Chemotherapy or radiation exposure
• Klinefelter syndrome variants 1

Less Common but Important:

• FSH-secreting pituitary adenoma (rare but critical to exclude) 6, 7
• Myotonic dystrophy 1
• Sickle cell disease 1
• Adrenoleukodystrophy 1

Recommended Diagnostic Work-Up

Step 1: Confirm the Hormonal Pattern

• Repeat FSH, LH, and total testosterone (morning, fasting) to confirm persistent elevation
• Measure free or bioavailable testosterone (may be low-normal despite normal total testosterone)

Step 2: Assess Fertility Status

If the patient has any interest in current or future fertility 4:

• Semen analysis is mandatory—elevated FSH typically indicates impaired spermatogenesis 4, 8
• Testicular examination: assess volume (normal 15-25 mL), consistency, and symmetry
• If severe oligospermia (<5 million/mL) or azoospermia: order karyotype and Y-chromosome microdeletion testing 4

Step 3: Exclude Pituitary Pathology

Critical pitfall: While rare, FSH-secreting pituitary adenomas can present with this exact pattern 6, 7:

• Assess testicular size carefully: If testes are enlarged (>25 mL), strongly suspect FSH-secreting adenoma 6
• Measure serum inhibin if available (elevated in FSH-secreting adenomas) 6
• Consider pituitary MRI if:
  • Testicular enlargement present
  • Disproportionately elevated FSH (>2-3× upper limit)
  • Any visual symptoms or headaches
  • Inhibin levels elevated

Step 4: Identify Underlying Testicular Pathology

• Testicular ultrasound: evaluate for masses, microlithiasis, atrophy, or asymmetry
• History: prior infections, trauma, cryptorchidism, chemotherapy, radiation
• Screen for systemic conditions: diabetes, HIV, chronic kidney disease 1

Step 5: Additional Hormonal Assessment

• Prolactin: if any symptoms of hypogonadism or to exclude mixed pituitary pathology 4
• Estradiol: if gynecomastia or breast symptoms present 4
• Thyroid function: hypothyroidism can affect gonadotropin secretion

Clinical Implications and Management Considerations

Fertility Concerns

This pattern strongly predicts impaired spermatogenesis 4, 2, 8:

• FSH >2× upper limit of normal typically indicates severe seminiferous tubular damage
• Even with normal sperm counts, elevated FSH suggests reduced testicular reserve 2
• Counsel about potential progressive decline in fertility
• Consider sperm banking if future fertility desired

Testosterone Replacement Therapy Considerations

Exercise caution before initiating TRT:

• The "normal" testosterone may decline over time as testicular compensation fails
• If fertility is desired, TRT is contraindicated (will suppress spermatogenesis further) 4
• If TRT becomes necessary, the patient already has compromised testicular function and may be at higher risk for complete suppression

Monitoring Strategy

For patients not requiring immediate intervention:

• Recheck FSH, LH, testosterone every 6-12 months
• Monitor for development of symptoms (fatigue, decreased libido, erectile dysfunction)
• Reassess fertility parameters if relevant
• Watch for testicular atrophy on examination

Common Pitfalls to Avoid

1. Assuming "normal testosterone = no problem": The elevated gonadotropins indicate underlying pathology requiring investigation 1, 2

2. Missing FSH-secreting adenomas: Always assess testicular size—enlargement is the key clinical clue 6

3. Initiating TRT without fertility assessment: This permanently compromises fertility in men with already impaired spermatogenesis 4

4. Failing to obtain semen analysis: FSH elevation predicts impaired spermatogenesis, but severity varies 4, 8

5. Not recognizing this as progressive: Compensated hypogonadism may decompensate over time, requiring longitudinal monitoring