Azoospermia — Zero Sperm on Semen Analysis
Azoospermia means no sperm on centrifuged sample review.
- ~15%: Men affected by infertility (of couples trying to conceive)
- ~10%: Azoospermia among infertile men (complete absence of sperm)
- 2: Confirmatory samples required (centrifuged specimens, separate days)
- ~40/60: Obstructive vs non-obstructive split (rough clinical proportion)
Confirming true azoospermia
Centrifuge the pellet and check twice before labeling.
Two broad causes
Blocked outflow versus failed sperm production upstream.
Why hormones matter next
Blood hormone levels separate the two causes fast.
The Hormone Panel — FSH, LH, Testosterone, Inhibin B
Four hormones map the hypothalamic-pituitary-testicular axis.
- 1.5–12.4: FSH reference range (mIU/mL, adult male)
- 80–300: Inhibin B reference range (pg/mL, adult male)
- 300–1000: Total testosterone reference (ng/dL, adult male)
- 1–3: Test turnaround (days typical lab result)
FSH drives spermatogenesis
Pituitary FSH stimulates Sertoli cells to nurse sperm.
Inhibin B signals tubule mass
Sertoli cells secrete inhibin B, reflecting tubule health.
LH and testosterone track Leydig cells
LH drives Leydig cells to make testosterone locally.
Normal FSH, Normal Inhibin B — Intact Spermatogenesis, Blocked Outflow
Sperm are made normally but cannot exit the tract.
- Normal: FSH in obstructive azoospermia (typically under 8 mIU/mL)
- Normal: Inhibin B in obstructive azoospermia (typically over 150 pg/mL)
- Normal: Testicular volume (usually preserved bilaterally)
- 3: Common blockage sites (epididymis, vas, ejaculatory duct)
Tubules stay active
Healthy Sertoli signaling keeps FSH and inhibin B normal.
Sperm back up behind a block
Vasectomy, infection, or absence of the vas can obstruct.
Next step options
Surgical reconstruction or sperm retrieval can restore fertility.
Elevated FSH, Low Inhibin B — Primary Testicular Failure
Tubules stop producing sperm, so feedback hormones shift.
- Elevated: FSH in non-obstructive azoospermia (often over 15 mIU/mL)
- Low: Inhibin B in non-obstructive azoospermia (often under 100 pg/mL)
- Reduced: Testicular volume (small, soft testes common)
- 4: Common causes (genetic, varicocele, toxin, idiopathic)
Sertoli cells fail to signal
Fewer functioning tubules make less inhibin B overall.
Pituitary compensates with more FSH
Lost negative feedback pushes FSH secretion upward.
Karyotype and genetic testing follow
Klinefelter syndrome and Y-microdeletions are commonly screened.
Hormone Pattern Guides the Next Diagnostic Step
The FSH-inhibin B pattern sets the entire workup path.
- TESA/TESE: Obstructive next step (or surgical duct reconstruction)
- Micro-TESE: Non-obstructive next step (plus genetic counseling)
- Selective: Testicular biopsy role (used when pattern is unclear)
- >90%: Sperm retrieval success, OA (versus lower in NOA)
Obstructive path
Retrieve sperm surgically or repair the blocked duct.
Non-obstructive path
Micro-TESE searches for rare pockets of active tissue.
When the pattern is unclear
Testicular biopsy directly answers what hormones cannot.