MTHFR and Infertility: Hypermethylation of MTHFR has been found in testes from males affected by non-obstructive azoospermia and in sperm cells from males affected by oligozoospermia and teratozoospermia as well as in idiopathic infertile males (Khazamipour et al., 2009; Wu et al., 2010; Botezatu et al., 2014; Karaca et al., 2017).