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, Tsetskhladze ZR, Kristesashvili J, Pirtskhalava M, Urjumelashvili M, Tchiokadze S, Vakhania M, Parunashvili N, Asanidze A 2025 · International journal of fertility & sterility | 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, Zhang Y, Pan Y, Zhang Y, Liu M, Huang Y, Xiao Y, Mo W, Jiao J, Wang X, Tian D, Yang L, Ma Y 2021 · Reproductive biology and endocrinology : RB&E | 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. |
| Li Y, Zhu H, Liu M, Zeng Z, Zeng Y, Xu X, Ye M 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, Kumar P 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 · Genetics and molecular research : GMR | 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, Assmann TS, Martínez P, Cerpa L, Calfunao S, Echiburú B, Maliqueo M, Crisosto N, Salas-Pérez F 2024 · Nutrients | observational | contradicts | low | Chilean case-control, 29 PCOS vs 29 controls, TaqMan genotyping of MTHFR C677T (rs1801133). Clean null: T allele frequency 0.48 in PCOS vs 0.50 in controls (points away from the claim); T carriers 21/29 vs 23/29 (dominant p=0.759), TT 7 vs 6 (recessive p=0.999); authors: 'the MTHFR A1298C and C677T polymorphisms were not associated with PCOS'. No OR/CI reported. Very small; authors note 'limited statistical power'. Non-Asian (Chilean) population. |
| Santos TBD, Paula HK, Balarin MAS, Silva-Grecco RL, Lima MFP, Resende EAMR, Gomes MKO, Cintra MTR 2019 · Archives of endocrinology and metabolism | 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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