What FSH (Follicle-Stimulating Hormone) level indicates testicular failure and azoospermia?

FSH Levels and Azoospermia: Diagnostic Considerations

There is no specific FSH threshold that definitively indicates azoospermia, as FSH levels do not accurately predict the presence of spermatogenesis in azoospermic patients undergoing testicular sperm extraction (TESE). 1

Relationship Between FSH and Spermatogenesis

• FSH levels are generally negatively correlated with the number of spermatogonia 1
• Normal FSH reference range is typically 1.5-8 mIU/ml 2
• However, the European Association of Urology (2025) specifically states that for azoospermic patients undergoing TESE, FSH levels do not accurately predict the presence of spermatogenesis 1
• Men with maturation arrest on histology can have normal FSH and testicular volume despite having azoospermia 1

Clinical Significance of Elevated FSH

While no absolute threshold exists, research suggests:

• FSH levels >14.6 mIU/mL predict poor outcomes for microsurgical testicular sperm extraction (micro-TESE) in non-obstructive azoospermia with a sensitivity of 83.5% and specificity of 80.3% 3
• Even FSH levels >4.5 IU/L have been associated with abnormal semen parameters including sperm concentration and morphology 4
• Increasing FSH levels correlate with the appearance of Sertoli cell-only tubules, with mean values of 16.0 IU/L observed in patients with bilateral or unilateral total Sertoli cell-only syndrome 5

Diagnostic Algorithm for Azoospermia Evaluation

1. Initial assessment:

   • Complete semen analysis with centrifugation to confirm azoospermia
   • Measure serum FSH, LH, and testosterone 1, 2

2. Interpretation of FSH results:

   • Normal FSH (1.5-8 mIU/ml): May indicate obstructive azoospermia but does not rule out non-obstructive causes
   • Elevated FSH (>8 mIU/ml): Suggests primary testicular failure/non-obstructive azoospermia
   • FSH >14.6 mIU/ml: Associated with poor sperm retrieval outcomes in micro-TESE 3

3. Additional diagnostic steps:

   • Genetic testing (karyotype, Y-chromosome microdeletion analysis) for men with non-obstructive azoospermia 1, 2
   • Testicular volume assessment via physical exam or ultrasound 1
   • Consider measuring inhibin B (levels <67 pg/mL correlate with sperm retrieval failure) 6

Important Caveats

• Genetic factors impact FSH interpretation: Y-chromosome microdeletions in AZFa and AZFb regions predict poor sperm retrieval regardless of FSH levels 1, 2
• Histological variation: Men with maturation arrest can have normal FSH despite severe spermatogenic dysfunction 1
• Testosterone/FSH ratio: A decreasing testosterone/FSH ratio correlates with abnormal semen parameters and may provide additional diagnostic value 4
• Anti-Müllerian hormone (AMH): Lower preoperative serum AMH levels are associated with higher likelihood of positive sperm retrieval outcomes in micro-TESE 1

FSH should be considered one component of a comprehensive evaluation rather than a standalone diagnostic marker for azoospermia. While elevated FSH suggests testicular failure, normal FSH does not exclude severe spermatogenic dysfunction.