Table 1. The search strategy summary.

Items	Specification
Date of search	February 21, 2024
Database searched	PubMed
Search terms used	“MTHFR gene polymorphism”, “DNA methylation”, “HHcy”, “male infertility”, and “ED”
Timeframe	Between 2000 and 2023
Inclusion criteria	English and Chinese language studies were included. Peer-reviewed published articles were prioritized
Selection process	Each author was independently involved in literature search. The primary author (Z.X.) reviewed all included articles

Relevant important references are listed in Table 2. MTHFR, methylenetetrahydrofolate reductase; HHcy, hyperhomocysteinemia; ED, erectile dysfunction.