MTHFR and the Thyroid

As you will know from our other posts on this topic, the MTHFR gene is responsible for producing the MTHFR enzyme. When the gene is mutated, the enzyme produced does not function correctly. This incorrect function has an impact on our thyroid health and our ability to heal (because managing hypothyroidism or any other autoimmune disease isn’t tough enough!).

Conversion of T4 to T3

The Thyroid System

Unfortunately the relationship between MTHFR and the thyroid, once out of whack, can be a vicious cycle of negative impacts.

At its most basic level, hypothyroidism means low levels of thyroxine (T4) in the body. When we have a MTHFR gene mutation, it becomes more difficult for the body to convert T4 into T3.

But that doesn’t matter right? The doctor will just prescribe T3 to address the problem of an underactive thyroid…Unfortunately, this is not the case. Taking T3 in isolation ignores the body’s problem with producing T4. It’s almost like a band aid affect, as T4 is important for a number of bodily functions (but you need to make sure your body can convert the T4 to the right T3. If it converts to reverse T3 you could experience even worse problems).

T4 is responsible for producing our body’s active form of Vitamin B2, FAD (or flavin adenine dinucleotide if you want to get technical). In order for our body to use Vitamin B2 it must be converted to FAD, but if we don’t have enough T4 then we can’t convert it. Consequently the levels of FAD in our body is reduced.

FAD is important because the MTHFR enzyme relies on adequate levels of FAD to do its job properly! When FAD levels are reduced, the MTHFR enzyme slows down. A sluggish MTHFR enzyme leads to low levels of methylfolate and low SAMe.

SAMe is responsible for maintaining immune responses. Therefore when SAMe gets low, the immune responses start to get out of control. And the cycle starts again.

Adrenal HealthWhat is Adrenal Fatigue

Adrenal health, thyroid problems and methylation are all interrelated. When one doesn’t function properly, the others also won’t function properly.

As we discuss above, T4 is required to convert Vitamin B2 into FAD. And FAD is important because it controls the functioning of the MTHFR enzyme. When you can’t convert Vitamin B2 into FAD, you can become Vitamin B2 deficient.

Vitamin B2 is important for adrenal health as it helps to support the strong functioning of them in the face of thyroid issues. So not only does MTHFR impact thyroid health, it also has an impact on adrenal health.


Methylation is also important for the production of glutathione. Glutathione is our body’s protector – it is responsible for controlling the level of inflammation in our body and detoxifying any toxins we have come across. It also helps to regulate our body’s nitric oxide cycle which is essential for a healthy functioning immune system.

When there is a MTHFR gene mutation, synthesis of glutathione is compromised. As a result, the level of glutathione required to maintain its optimum functioning is reduced. Lower glutathione means a reduced ability to detox and fight inflammation, which all have an impact on thyroid health and our ability to heal and manage autoimmune diseases.