We do not see patients for MTHFR testing in clinic, or to assist in the interpretation of private MTHFR testing results.
The MTHFR gene encodes an enzyme which converts homocysteine to methionine. Genetic variations in MTHFR can lead to impaired function of this enzyme, which may result in mild increased homocysteine levels, particularly in individuals who are folate deficient. However, the health implications of this remain unclear.
There are some variants/’polymorphisms’ in MTHFR which are commonly found in the general population. It is estimated that ~10% of individuals in the UK & Ireland are homozygous for the C667T variant (“TT homozygous”). A1298C is another commonly observed MTHFR polymorphism.
There have been many studies exploring the relationship between MTHFR variants and a multitude of health disorders. Among C677T homozygotes, who have demonstrable elevation in homocysteine levels, there may be a slightly increased risk of venous thrombosis and recurrent pregnancy loss. However, the absolute risk increase is small, and the American College of Medical Genetics (ACMG) currently do NOT recommend MTHFR testing as part of the clinical evaluation of thrombophilia or recurrent pregnancy loss.
Some studies have also suggested that women who are C677T homozygotes are at increased risk of having a child with a neural tube defect, particularly if the baby is also a C667T homozygote. However, again, the absolute increase is small. At present, pregnant women who carry the variants described are recommended to take the standard dose of folic acid (in the absence of any other indication for high dose folic acid). Substituting with other folates, such as 5-MTHF, is NOT recommended.
Overall, we would reassure patients who carry these common variants that this is extremely common in the general population, and based on the scientific evidence currently available, we would not expect this to have significant implications for their health. Furthermore, we would not recommend any specific treatments or supplements.
Please note that these common MTHFR variants/polymorphisms would not be associated with very high homocysteine levels. If your patient has very high homocysteine levels and/or other features suggestive of Homocystinuria, then they may need referral to an appropriate specialty (e.g. Clinical Biochemistry).