Most people with hypothyroidism have Hashimoto’s, which is an autoimmune condition where the immune system attacks and damages the thyroid gland. But while Hashimoto’s is the number one cause of hypothyroidism, certain nutrients are important for the production of thyroid hormones. As a result, having a moderate to severe deficiency in any of these nutrients can also lead to hypothyroidism. In addition to discussing the nutrients which are important for thyroid hormone production in this blog post, I’m also going to discuss some nutrients which play a role in converting T4 into T3, as well as supporting the thyroid hormone receptor.
Nutrients That Support Thyroid Hormone Production
1. Iodine. In the world of thyroid health there is a lot of controversy surrounding iodine. While iodine can potentially trigger or exacerbate the autoimmune response in those people with Hashimoto’s thyroiditis, there is no question that iodine is important for thyroid hormone production. As a result, a moderate to severe iodine deficiency can cause hypothyroidism. Iodine specifically combines with tyrosine to form T4 and T3. There are four iodine atoms in thyroxine (T4), and three iodine atoms in triiodothyronine (T3).
The question many people with hypothyroidism have is whether or not they should supplement with iodine. Some healthcare practitioners advise everyone with hypothyroidism to avoid iodine supplementation, while others will encourage their patients to supplement with iodine. In my opinion, any mineral deficiency should eventually be corrected, but there is no doubt that not everyone does well with iodine. Before anyone supplements with iodine I would recommend conducting a urinary test for iodine , and even if you are deficient I would take at least a month or two to increase your antioxidant status. It’s also wise to work with a competent natural healthcare practitioner before supplementing with iodine.
2. Iron. Thyroid peroxidase is an enzyme that plays a role in the production of both T3 and T4. Thyroid peroxidase converts iodide to iodine, and as I mentioned earlier, the iodine in turn combines with tyrosine, which forms T4 and T3. As for why iron is important, the reason for this is because thyroid peroxidase requires iron to function properly. Thus, an iron deficiency can have a negative effect on thyroid hormone metabolism by reducing the activity of this enzyme (1)  (2) .
I recommend an iron panel (ferritin, serum iron, iron saturation, TIBC) to just about all of my patients. While iron supplementation might be required if someone is deficient in iron, this isn’t always the case. It depends on the cause of the deficiency, as well as how severe the iron deficiency is. Since vitamin C and stomach acid help with iron absorption, many times it makes sense to have the person supplement with vitamin C and do things to improve stomach acid production, such as consume apple cider vinegar, bitter herbs, and/or betaine HCL.
It’s also important to mention that you can’t rely on the lab reference ranges when determining if someone has an iron deficiency. I’ve seen many cases where someone’s ferritin or iron saturation was borderline low, yet was ignored by the physician who ordered the test. In my book “Hashimoto’s Triggers ” I dedicate an entire chapter discussing both the lab reference range and optimal reference range of many different blood markers, including those in an iron panel.
3. Tyrosine. You already know the importance of tyrosine in thyroid hormone production, and how it combines with iodine to form T4 and T3. While one can choose to take a tyrosine supplement, I wouldn’t recommend doing this unless a tyrosine deficiency has been confirmed. But of course it’s a good idea to make sure you’re getting sufficient tyrosine from your diet, and some food sources include chicken, turkey, fish, and eggs, although there are also vegetarian sources (i.e. avocados, spinach, and seaweed).
How can you test for a tyrosine deficiency? Although I can’t say that I commonly recommend amino acid testing to my patients, there are specialty labs that offer amino acid panels. These panels not only test for tyrosine, but for other amino acids as well. Genova Diagnostics is one company that offers such testing.
I’d like to briefly summarize the importance of these three nutrients, as in the thyroid epithelial cell, iodide is converted to iodine, and this is catalyzed by the enzyme thyroid peroxidase, which as I mentioned earlier, is dependent on iron. Iodine then combines with tyrosine to form T4 and T3. So if there is a moderate to severe deficiency in any of these nutrients there is a good chance it will eventually impact thyroid hormone production.
The Role of Selenium in Thyroid Hormone Conversion
I’ve written past blog posts where I discussed factors that affect the conversion of T4 to T3 . But just to summarize, the thyroid gland manufacturers mostly thyroxine (T4), and this gets converted into triiodothyronine (T3), which is the active form of thyroid hormone. Approximately 60% of this conversion takes place in the liver, while approximately 20% takes place in the gut. As a result, having an unhealthy liver and/or gut can affect the conversion of T4 to T3.
The deiodinases are enzymes that activate or inactive thyroid hormone. There are 3 main types of deiodinases, including deodinase type I, deodinase type II, and deodinase type III. The type 1 and type II deiodinase enzymes are responsible for the conversion of T4 to T3. On the other hand, the type III deiodinase enzyme is involved in the inactivation of T4 and T3. A selenium deficiency can decrease the activity of type I and type II deiodinases, which can result in a decreased conversion of T4 into T3 (3)  (4) .
It’s also worth mentioning that a few studies have shown that selenium supplementation (200 mcg) can decrease thyroid peroxidase (TPO) antibodies (5)  (6) . Selenium is a cofactor of glutathione peroxidase, which can decrease oxidative stress, and thus help with the autoimmune response. So having healthy selenium levels can not only play a role in T4 to T3 conversion, but can also help minimize the damage done to the thyroid gland by the immune system for those who have Hashimoto’s.
Nutrients That Support the Thyroid Hormone Receptor
Whereas overt hypothyroidism is characterized by an elevated TSH and low thyroid hormone levels, thyroid hormone resistance  is characterized by a normal or elevated TSH along with elevated free T3 and/or free T4 levels. While there are a few different factors that can cause thyroid hormone resistance, certain nutrient deficiencies can play a role, specifically vitamin A and zinc:
1. Vitamin A. The binding of T3 to the thyroid receptor is retinoic acid-dependent (7) . As a result, having a vitamin A deficiency can be a factor in thyroid hormone resistance. Some people are understandably concerned about vitamin A toxicity, and thus, when supplementing they will choose to take beta carotene. Just keep in mind that some people have problems converting beta carotene into active vitamin A (8) .
2. Zinc. Zinc appears to play a role in the health of the T3 receptor (9) , and so it would make sense that a zinc deficiency can cause thyroid hormone resistance.
So hopefully you have a better understanding of the different nutrients required for thyroid hormone production, the conversion of T4 to T3, and for supporting the thyroid hormone receptors. Being deficient in any of these can result in subclinical or overt hypothyroidism. Please feel free to share your experience regarding these nutrients in the common section below.