Table 1. Etiologies for non-obstructive azoospermia & obstructive azoospermia.

Etiology class	Pituitary or hypothalamic mediated NOA	Testicular mediated NOA	OA
Genetic & congenital	Kallman syndrome	KS (XXY); Y-chromosome microdeletion (AZF a, b or c); cryptorchidism	CBAVD (CFTR mutation)
Acquired	Pituitary tumor, radiation, extirpation; exogenous androgens	Testicular cancer; malignancy; chemotherapy; abdominal or pelvic radiation; orchitis; testicular torsion; varicoceles	Vasectomy; ejaculatory duct obstruction; epididymitis; iatrogenic: orchidopexy or hydrocelectomy (with obstructing suture or compression), inguinal hernia repair, spermatocelectomy

NOA, non-obstructive azoospermia; OA, obstructive azoospermia; KS, Klinefelter syndrome.