MTHFR and varicocele: A meta-analysis by Mostafa et al. included 19 studies (1826 varicocele patients, 2070 controls, and 263 infertile men without varicocele) and found high heterogeneity and no conclusive genetic associations despite the analysis of GSTM1, GSTT1, NOS3, ACP1, NQO1, PRM1, PRM2, MTHFR, POLG, HSP90, and even mitochondrial genes [13].