Metabolic & Cardiometabolic
MTHFR C677T increases PCOS
Part of: • MTHFR C677T
📅 Last reviewed: 2026-07-15 ⓘ
Evidence ladder
How far up the ladder this claim has climbed. A high consensus on a low rung means "consistent so far," not "proven in people."
Top evidence so far: All trials, pooled (Meta-analysis)
How the studies fall
What the evidence shows
The MTHFR C677T T-allele modestly increases PCOS risk.
The evidence (7)
| Source | Grade | Stance | Quality | Finding |
|---|---|---|---|---|
| Asanidze E et al 2025 · study_type: observational | observational | supports | low | Georgian case-control, n=177 (96 PCOS/81 controls). C677T + A1298C prevalence sig. higher in PCOS vs controls (P<0.05); no pooled OR/CI given; small single-country sample. |
| Feng W et al 2021 · study_type: observational | observational | contradicts | moderate | Southern Chinese case-control, n=450 (150 PCOS/300 controls). A1298C significantly associated with PCOS (dose-dependent, OR up to 3.76); C677T not reported as significant — implied null for C677T specifically. |
| Zhang J, et al. 2020 · Medicine (Baltimore) | meta-analysis | supports | moderate | MTHFR C677T allele OR 1.40 (1.27-1.53), homozygous OR 1.90 (1.55-2.32) for PCOS — larger effect than the prior 2025 meta (OR 1.18). |
| Rai V et al] # corrected 2026-08-17 from PubMed; was [et al. 2025 · Ind J Clin Biochem | meta-analysis | supports | moderate | MTHFR C677T T-allele vs C: OR 1.18 (1.01–1.38) for PCOS. |
| mthfr-pcos-china-2016 2016 | observational | supports | moderate | Case-control (244/257, China): TT genotype OR 1.84 (1.05-3.26); T allele OR 1.38 (1.06-1.81) for PCOS. |
| Carrasco-Cabezas M et al 2024 · study_type: observational | observational | tested-null | low | Chilean case-control (PCOS vs controls). MTHFR C677T and A1298C polymorphisms 'were not associated with PCOS' — explicit null finding in a Caucasian/Hispanic (non-Asian) population. |
| Santos TBD et al 2019 · study_type: observational | observational | contradicts | low | Brazilian case-control, n=203 (99 PCOS/104 controls). C677T alone not significant; only the T-C (C677T-A1298C) haplotype was associated, and in the PROTECTIVE direction (OR=0.19) toward controls. |
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