What FSH (Follicle-Stimulating Hormone) levels indicate azoospermia?

FSH Levels Indicating Azoospermia

FSH levels greater than 7.6 IU/L strongly suggest non-obstructive azoospermia, while FSH levels below this threshold typically indicate obstructive azoospermia or oligospermia. 1

Relationship Between FSH and Spermatogenesis

• FSH levels are negatively correlated with the number of spermatogonia, meaning higher FSH generally indicates decreased sperm production 2, 1
• Men with non-obstructive azoospermia (NOA) usually present with low testicular volume, normal sperm volume, and elevated FSH values 1, 3
• An FSH level of 11 IU/L is consistent with primary testicular dysfunction, suggesting significant impairment of spermatogenesis 1

Diagnostic Patterns and Clinical Implications

• Physical examination showing testicular atrophy combined with FSH >7.6 IU/L strongly suggests non-obstructive azoospermia 1, 3
• Serum FSH helps differentiate between obstruction and spermatogenetic dysfunction as possible causes of azoospermia 4
• The probability of finding sperm decreases significantly as FSH levels increase, with recent research suggesting an FSH cutoff of 15.3 mIU/mL as predictive for potential sperm identification in semen 5

Important Caveats and Limitations

• FSH levels alone cannot definitively predict sperm retrieval success in all cases of non-obstructive azoospermia 2, 1, 6
• Men with maturation arrest on testicular histology can have normal FSH and testicular volume despite having severe spermatogenic dysfunction 2, 3
• Even with markedly elevated FSH levels (>20 mIU/mL), sperm retrieval may still be possible in approximately 24% of cases 7
• Case reports document successful pregnancies in patients with FSH levels as high as 38.7 mIU/mL through testicular sperm extraction and intracytoplasmic sperm injection 8

Diagnostic Algorithm

1. Confirm azoospermia with at least two properly performed semen analyses 6

2. Measure serum FSH, testosterone, and LH levels 2, 3

3. Interpret FSH results:

   • FSH <7.6 IU/L: Suggests obstructive azoospermia, especially with normal testicular size 1
   • FSH >7.6 IU/L: Suggests non-obstructive azoospermia, especially with testicular atrophy 1
   • FSH >15.3 mIU/mL: Lower probability of finding sperm in ejaculate even with repeated analyses 5
   • FSH >20 mIU/mL: Significantly reduced but not zero probability (~24%) of successful sperm retrieval 7

4. For elevated FSH, proceed with genetic testing (karyotype and Y-chromosome microdeletion analysis) 1, 6

5. Consider testicular biopsy or sperm extraction techniques for definitive diagnosis and potential assisted reproduction 1, 9