Idiopathic non-obstructive azoospermia and cryptozoospermia are severe forms of male infertility in which sperm production is absent or extremely low and the cause is often unknown. This retrospective observational study examined whether mitochondrial DNA variants, particularly the MT-ND1 m.3700G\>A variant, are associated with impaired sperm production in Chinese men.
Existing clinical records and available biospecimens from affected men, eligible family members, and fertile controls were analyzed to assess familial inheritance patterns, the frequency of the variant, and its association with infertility phenotypes. No study-related treatment or intervention was provided to human participants.