Male gonad tissue samples collected from patients with NOA harbouring a mutation in the TKTL1 gene showed a significant downregulation in HERC5, CSF3, HES1 and HSPA1B genes, compared with patients with azoospermia without mutation in the TKTL1 gene (negative control) as well as control samples with normal spermatogenesis. The gene discussed is TKTL1; the disease is Azoospermia.