30 of the most common questions about DNA, MTHFR, COMT, hormones, and methylation — answered directly by a credentialed geneticist. No fluff, no upsells, no buried disclaimers.
Written by Izel · BSc Genetics & Bioengineering · 10+ years experience · Genova Lab
MTHFR (methylenetetrahydrofolate reductase) is the enzyme that converts dietary folate into 5-methyltetrahydrofolate (5-MTHF), the active form your body uses for methylation reactions. The MTHFR gene has two clinically relevant variants: C677T (rs1801133) and A1298C (rs1801131), which reduce enzyme activity to varying degrees.
C677T affects the catalytic domain of the MTHFR enzyme and directly impairs folate-to-5MTHF conversion, primarily elevating homocysteine. A1298C affects the regulatory domain and primarily reduces BH4 (tetrahydrobiopterin) production, affecting neurotransmitter synthesis rather than homocysteine levels.
Heterozygous means you carry one normal copy and one variant copy of the gene. For MTHFR C677T heterozygous (genotype CT), enzyme activity is reduced by approximately 35%. Clinical impact is generally modest in healthy adults with adequate dietary folate.
Homozygous means both copies of the gene carry the variant. MTHFR C677T homozygous (genotype TT) reduces enzyme activity by approximately 70% and shows the strongest research associations with elevated homocysteine.
Compound heterozygous means you carry one copy of C677T and one copy of A1298C — one variant of each on different chromosomes. This combination reduces MTHFR enzyme activity by approximately 50-60% and is often more clinically significant than either homozygous state alone.
Methylfolate supplementation is the standard intervention for MTHFR C677T variants because it bypasses the impaired enzyme step. However, appropriate dose depends on your COMT genotype: COMT Met/Met carriers (slow catecholamine clearance) often experience anxiety symptoms with high-dose methylfolate. Baseline homocysteine measurement should precede supplementation decisions.
COMT (catechol-O-methyltransferase) is the enzyme that breaks down dopamine, norepinephrine, and epinephrine in the prefrontal cortex. The Val158Met polymorphism (rs4680) creates three genotypes: Val/Val (fast clearance, 'warrior'), Val/Met (intermediate), and Met/Met (slow clearance, 'worrier').
The 'warrior gene' is informal terminology for COMT Val/Val genotype. Val/Val carriers clear catecholamines approximately 3-4 times faster than Met variants, producing lower baseline prefrontal dopamine, superior stress resilience, and better tolerance of stimulants and methylated B vitamins.
The 'worrier gene' is informal terminology for COMT Met/Met genotype. Met/Met carriers clear catecholamines slowly, producing higher baseline prefrontal dopamine, superior baseline cognitive performance, but vulnerability to anxiety and overstimulation under acute stress.
Methylfolate increases SAM (S-adenosylmethionine) availability, which accelerates COMT-mediated catecholamine breakdown. In COMT Met/Met carriers with slow clearance, this floods the system with substrate the enzyme cannot process quickly enough, producing anxiety, irritability, and overstimulation symptoms.
Download your raw data from 23andMe (Settings → 23andMe Data → Access Your Data → Download Raw Data). Unzip the .txt file and open in any text editor. Search (Ctrl+F or Cmd+F) for rs1801133 (MTHFR C677T) and rs1801131 (MTHFR A1298C). The last column shows your genotype.
Yes. AncestryDNA's standard SNP array includes both rs1801133 (C677T) and rs1801131 (A1298C). The procedure for finding these variants is identical to 23andMe — download raw data, unzip, search the .txt file.
23andMe stopped reporting MTHFR in their consumer reports because the FDA restricted health-related claims for direct-to-consumer genetic tests. The underlying genotype data is still tested and available in the raw data download.
Homocysteine is an amino acid intermediate in the methionine cycle. When methylation is impaired (e.g., MTHFR variants, B12 deficiency, low riboflavin), homocysteine accumulates rather than being recycled. Elevated homocysteine is an established cardiovascular risk marker. Normal range is typically below 9 μmol/L.
MTHFR and COMT both use methyl groups from the same SAM pool. High-dose methylfolate supplementation drives SAM production, which accelerates COMT-mediated catecholamine breakdown. COMT genotype determines whether this acceleration is well-tolerated (Val/Val) or causes anxiety symptoms (Met/Met).
BH4 (tetrahydrobiopterin) is a critical enzyme cofactor required for the synthesis of serotonin, dopamine, norepinephrine, and nitric oxide. BH4 production is influenced by MTHFR A1298C (which affects regulatory function more than catalytic activity) and is supported by riboflavin (B2), vitamin C, and folinic acid.
CBS (cystathionine beta-synthase) upregulation variants increase the activity of the enzyme that pulls homocysteine into the transsulfuration pathway. Carriers can experience adverse symptoms from standard high-dose methylation protocols because the increased CBS activity floods the sulfur pathway downstream.
VDR Bsm1 (rs1544410) is a vitamin D receptor variant that affects intracellular vitamin D signaling. Carriers can maintain 'normal' blood vitamin D levels while showing blunted intracellular response — meaning standard dosing may be insufficient to achieve equivalent physiological effect.
MAOA (monoamine oxidase A) is the enzyme that breaks down serotonin, dopamine, and norepinephrine. The MAOA-uVNTR polymorphism creates 'high-activity' and 'low-activity' variants affecting neurotransmitter breakdown rate, with documented influences on mood, aggression, and stress response.
The genetic factors that determine functional testosterone status are: SHBG variants (rs6258, rs1799941) affecting binding globulin levels; CYP19A1 variants affecting aromatase activity and testosterone-to-estradiol conversion; AR CAG repeat polymorphism affecting androgen receptor sensitivity; and 11β-HSD1 variants affecting cortisol metabolism.
Functional androgen status in women is determined by: SHBG variants (binding globulin and free testosterone availability); CYP19A1 aromatase variants (testosterone-to-estradiol conversion); and AR CAG repeat polymorphism (androgen receptor sensitivity). Total testosterone often appears normal while free testosterone is functionally low.
The androgen receptor (AR) gene contains a CAG repeat polymorphism that determines receptor transcriptional efficiency. Shorter CAG repeats produce more sensitive androgen receptors; longer repeats produce less sensitive receptors. The same testosterone level can produce different functional effects depending on this repeat length.
PCOS has multiple genetic drivers depending on phenotype. Androgen-excess PCOS is driven by CYP11A1, CYP17, and AR variants. Insulin-resistant PCOS is driven by INSR, IRS1, and TCF7L2 variants. Inflammatory PCOS is driven by TNF-α, IL-6, and immune regulation variants. The phenotype determines the appropriate intervention.
No. IRS1 rs1801278 (Gly972Arg) is associated with reduced metformin response. This variant impairs insulin receptor substrate signaling and predicts poor response to metformin, which is why some PCOS patients see limited benefit from the standard pharmaceutical approach.
The most consistently replicated genetic associations with Hashimoto's thyroiditis are HLA-DR3 and HLA-DR5 (immune tolerance), CTLA4 rs231775 (T-cell regulation), PTPN22 rs2476601 (lymphocyte signaling), and selenoprotein gene variants (SELENOP, GPX1) affecting thyroid antioxidant defense.
The gluten-Hashimoto's connection is genotype-dependent. Strongest evidence is in carriers of both HLA-DQ2 or HLA-DQ8 coeliac variants and thyroid autoimmunity variants. For people without these HLA variants, strict elimination may produce limited benefit.
Clinical trial evidence supports 200mcg daily of selenomethionine for reducing anti-TPO antibodies in Hashimoto's thyroiditis. Selenium has a narrow therapeutic window — excess is toxic. Dosing should be informed by baseline selenium status and ideally selenoprotein gene variants.
No. Your MTHFR genotype is fixed at conception and does not change over your lifetime. What changes is the context — your baseline biomarkers (homocysteine), nutritional status, and downstream pathway demands — that determines whether the genotype is clinically expressed.
MTHFR variants are not a medical condition; they are common genetic polymorphisms. Approximately 40% of the global population carries at least one C677T variant copy. Whether they require clinical intervention depends on enzyme activity reduction, baseline homocysteine, dietary folate status, and interactions with other variants in the methylation network.
For most healthy adults with adequate dietary folate, MTHFR variants do not require medical intervention. Clinical consultation is warranted if you have elevated homocysteine, recurrent miscarriage history, cardiovascular risk factors, or symptoms that may relate to methylation dysfunction (mood disorders, chronic fatigue). For evidence-based interpretation of your full variant profile, a qualified geneticist or functional medicine clinician can help translate raw data into actionable protocols.
For personalised analysis of your raw DNA data, upload your 23andMe or AncestryDNA file and get a report built around your specific genome.
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