Amino acids and thyroid function

When managing hypothyroidism, many people assume that taking thyroid medication is enough to alleviate symptoms. However, in some cases, this approach doesn’t fully resolve issues. One key reason is that proper thyroid function depends on more than just medication - it requires the right nutrients, particularly amino acids, to support thyroid hormone conversion.

Understanding thyroid function: TSH, T4, and T3

Thyroid stimulating hormone (TSH)

Thyroid stimulating hormone (TSH) is produced to send signals from the pituitary gland, which feeds hormonal messages to the thyroid gland. Cells in the thyroid gland then produce thyroxine also known as T4.

Thyroxine (T4)

T4 consists of the amino acid tyrosine plus four iodine atoms. However, for the body to use thyroid hormones effectively, T4 must be converted into triiodothyronine (T3), the active form that regulates metabolism. This conversion primarily happens in the liver with the help of 5’-deiodinase enzymes. These enzymes remove one iodine atom from T4, transforming it into T3.

Once the conversion has happened, the release of energy can take place and this process is with the assistance of transport proteins. Critically, transport proteins require the correct nutrients (protein being part of this process) to be effective.

Why does T4 to T3 conversion fail?

An antioxidant known as glutathione (made up of three amino acids; cysteine, glycine, and glutamic acid) is utilised by the liver to deal with toxicity also known as free radicals. 

If we carry a lot of oxidative stress (free radicals), there may not be enough glutathione to deal with it, leading to challenged tissues and an inability to convert T4 to T3 due to a lack of amino acids.

Also, the amino acid L-methionine plays a vital role in the production of cysteine, so if this is in short supply, again the chain reaction is affected.

The link between amino acids and thyroid health

We have established that abundant amino acids are essential for a healthy thyroid, so where individuals may have diets low in protein, their thyroid health could be affected. Vegans, vegetarians, restricted eating through weight loss injections, gastric/bariatric intervention, and fussy eaters to name a few are risking depriving the liver and thyroid to work together as they are unable to bridge the gap through low protein.

Therefore, it is known that, in some cases, where the liver is unable to perform effectively (whether it be from clinical disease, medications, alcohol abuse, protein digestion issues such as leaky gut, lack of stomach acid (PPIs), NFLS or gluten intolerance), the build-up of toxins and the use of amino acids for detoxification could suffer, as the availability of amino acids for its functionality is challenged. In other words, the endocrine system is robbing Peter to pay Paul.

Key amino acids for thyroid function

The structure of protein is made up of amino acids arranged in different patterns. The body is unable to make amino acids on its own, so they have to be introduced through food.

Amino acids are split into two groups essential and non-essential. The non-essential amino acids can be produced by the body through the conversion of essential amino acids.

• L-Methionine - Essential for converting T4 to T3. Part of the synthesis of glutathione in the liver. Required for zinc and selenium absorption which are vital for thyroid health. Therefore, if you supplement the above hoping to improve your thyroid health, their effectiveness will be affected if methionine is low.
• Glutathione - Directly involved in converting T4 into T3. A powerful antioxidant that detoxifies the liver. Deficiency can lead to sluggish thyroid function.
• L-Phenylalanine - Forms another amino acid called tyrosine.
• Tyrosine - Once produced from phenylalanine, it continues on to be connected with iodine forming T4. Therefore, if tyrosine is in short supply, the T3 and T4 process will be decreased.
• L-Lysine - Essential for a healthy immune system so vulnerability to viruses can result if levels are low. As the toxicity through poor health rises, leading to an increase in free radicals, the use of methionine will increase (see above). Lysine is also important for the absorption of iron which, if poorly absorbed, can lead to chronic fatigue and anaemia. These are often seen in individuals with thyroid problems.
• Glutathione - We have gone full circle; this amino acid is formed with cysteine, glycine and glutamic acid. These antioxidants are needed by the liver to ‘clean up’ toxicity.

How to get enough amino acids

While supplementation is an option, a nutrient-rich diet is the best way to support thyroid function naturally. Amino acids can be derived through good sources of protein in food, such as:

• Animal-based proteins: Eggs, beef, lamb, venison, chicken, turkey, goat, fish, dairy products.
• Plant-based sources: Seeds, pulses, legumes (for those on plant-based diets, protein intake should be carefully managed to ensure sufficient amino acid diversity).

If dietary intake is inadequate, essential amino acid supplements may be beneficial. However, the body should still be encouraged to produce non-essential amino acids through conversion.

There are many other factors to consider but this article focuses on amino acid viability. Clearly, if there are indications of leaky guy, poor gut biome, use of medications, or challenged liver function, for example, then other support may be needed.