Men with non-obstructive infertility have been shown to carry microdeletions of AZF (Azoospermia Factor) sequences in their DNA, in the regions associated with spermatogenesis.

Three non-overlapping regions have been designated as AZFa, AZFb, and AZFc, and are directly implicated in the spermatogenesis.
(Mol. Hum. Reprod. 4:739-744).

*Reference : (Mol. Hum. Reprod. 4:739-744).