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Iron Deficiency and Hypothyroidism- How Iron Anemia Shuts Down The Thyroid

Iron deficiency can have a profound impact on thyroid function, causing disruptions in various critical aspects of thyroid health. Key processes affected by iron deficiency anemia include thyroid peroxidase activity, T4-T3 thyroid conversion, thyroid receptor inhibition, and iodine usage. In today’s article, I review not only how Iron deficiency contributes to hypothyroidism, but where we like to see optimal iron levels, what tests should be done to properly evaluation iron deficiency and finally how to address Iron deficiency when you have hypothyroidism. Let’s jump in!

Video Transcript 

Iron Deficiency Anemia and Hypothyroidism

One of the most important things I think someone with thyroid disease, Hypothyroidism, Hashimotos can do, is make sure their iron levels are in the optimal range by getting their Iron levels and ferritin levels checked 1-2x per year. Iron deficiency anemia is one of the most common nutrient deficiencies seen in patients with thyroid disease. It’s more common than a B12 deficiency, more common than Selenium deficiency, more common than magnesium deficiency, a zinc deficiency or even a vitamin D deficiency.

Not only is it common, but it’s almost completely missed by the overwhelming majority of doctors who treat patients with Thyroid disease. If this sounds important to you keep reading about Iron deficiency anemia and thyroid disease.

I’m Dr Hagmeyer and if you stay with me through this video, you’re going to learn why Iron is so important to your thyroid and maybe why it could be the single reason you’re still feeling like crap despite taking thyroid hormone medication. Have you been treated for hypothyroidism but still can’t get your TSH and Thyroid hormone levels to budge?

Or have you been prescribed Synthroid or Levothyroxine medication and no matter how much your doctor increases your dose your hair is still thinning, and you feel like a walking zombie?

Well, iron deficiency could be the missing link in your thyroid treatment. Both hypothyroidism and iron deficiency share some similar symptoms that include:

  • Fatigue
  • Hair loss
  • Dry skin
  • Sensitivity to the cold
  • Reduced peripheral circulation.
  • Brain fog
  • Muscle weakness

Patients who have hypothyroidism deserve special attention and treatment if their iron stores are low because of how important iron is for thyroid hormone function.

4 Ways Iron Deficiency Contributes to Hypothyroidism

Iron anemia and thyroid disease

#1 Thyroid Peroxidase.

Without iron you can’t activate the enzyme Thyroid peroxidase. Which is absolutely critical to thyroid hormone production. Thyroid peroxidase (TPO) is an enzyme made by the thyroid gland and what it does is, it takes Iodide convert it into Iodine and adds tyrosine to protein thyroglobulin and that’s how Thyroid hormones are made. You don’t need to memorize all of that but what you should know is that without Iron you can’t make Thyroid Hormones. If your body is low in iron, the enzyme responsible for this can be reduced in activity up to 50%. (*), (*),(*),(*)


Recent studies have shed light on the relationship between iron deficiency anemia and thyroid peroxidase (TPO) levels, an enzyme essential for thyroid hormone synthesis. This comprehensive article explores the effects of iron deficiency anemia on TPO levels, including the underlying mechanisms, potential diagnostic challenges, and the significance of proper management. Understanding this relationship can empower individuals and medical professionals to take proactive steps in addressing these conditions for optimal health.

Thyroid peroxidase (TPO) is a key enzyme involved in the synthesis of thyroid hormones, namely, thyroxine (T4) and triiodothyronine (T3).

Located within the thyroid gland, TPO facilitates the iodination of tyrosine residues, a necessary step for the synthesis of thyroid hormones.

Proper thyroid hormone production is crucial for maintaining a healthy metabolism, regulating body temperature, and supporting various bodily functions. Disruption in TPO levels can impair thyroid hormone synthesis, leading to thyroid disorders such as hypothyroidism or Hashimoto’s thyroiditis, an autoimmune condition.

Accurate diagnosis of iron deficiency anemia and its impact on TPO levels can be challenging due to overlapping symptoms with other conditions. Fatigue, weakness, and hair loss are common symptoms associated with both iron deficiency anemia and thyroid disorders. Healthcare professionals often rely on blood tests to assess iron levels, such as serum ferritin, transferrin saturation, and hemoglobin concentration.

Additional thyroid tests, including TPO antibody levels and thyroid hormone profiles, are required to evaluate the impact of iron deficiency anemia on TPO levels.

Proper interpretation of test results alongside a thorough clinical evaluation is essential to accurately diagnose and address these conditions.

Ashraf, TS, De Sanctis, V, Yassin, M, Wagdy, M & Soliman, N, 2017, ‘Chronic anemia and thyroid function’ Acta BioMedica, vol.88, no.1, pp.119–127, doi:10.23750/abm.v88i1.6048

iron deficiency anemia and thyroid

#2 T4-T3 Conversion

Iron is needed to convert T4 into T3. If you are iron deficient your body cant take inactive T4 and convert it into active T3.

Iron deficiency anemia and thyroid disorders are prevalent health conditions affecting millions worldwide. Recent studies have highlighted the relationship between iron deficiency anemia and alterations in the conversion of thyroxine (T4) to triiodothyronine (T3) in the thyroid gland.

The thyroid gland produces two essential hormones, thyroxine (T4) and triiodothyronine (T3) and its important to test BOTH of these when you have thyroid disease.

While T4 is the primary hormone secreted by the thyroid gland, it is relatively inactive. The conversion of T4 to the more biologically active T3 occurs primarily in peripheral tissues. This conversion is catalyzed by the deiodinase enzymes, with the most significant conversion occurring in the liver and other tissues.

The conversion of T4 to T3 is crucial for maintaining a healthy metabolism, promoting growth and development, and supporting various bodily functions. Any disruption in this conversion process can lead to imbalances in thyroid hormone levels and potential health complications.

When iron levels are low, these enzymes’ activity is compromised, leading to reduced T3 production and higher levels of the inactive T4 hormone. As a result, individuals with iron deficiency anemia may experience symptoms of hypothyroidism, such as weight gain, fatigue, and cognitive impairment.

The disruption in T4 to T3 conversion influences the body’s metabolic rate, affecting energy levels and overall well-being.

Additional thyroid tests, including T4, T3, and thyroid-stimulating hormone (TSH) levels, are required to evaluate the thyroid’s impact on T4 to T3 conversion. A comprehensive clinical evaluation, alongside proper interpretation of thyroid test results, is crucial to accurately diagnose and treat these conditions.

iron deficiency anemia and thyroid

#3. Thyroid Receptor Binding Inhibition

Having an iron deficiency reduces the way T3 binds to thyroid receptors. You can have plenty of T3 but if your iron levels are low, T3 can’t bind to its receptor and can’t unlock the receptor and allow your body to benefit from T3. (*)

Thyroid receptors are specialized proteins located in various tissues that bind to thyroid hormones, allowing them to regulate gene expression and metabolic activity. Iron is a vital cofactor for the proper functioning of these receptors, as it plays a role in their synthesis and maintains their stability. When iron levels are low, these receptors may become less effective, impairing the responsiveness of cells to thyroid hormones and potentially leading to a range of symptoms and health issues.

Iron deficiency can disrupt thyroid receptor activity through multiple mechanisms. Firstly, iron is necessary for the synthesis of thyroid hormones, including thyroxine (T4) and triiodothyronine (T3).

Inadequate iron levels can reduce hormone production, leading to decreased activation of thyroid receptors. Additionally, iron deficiency can trigger the activation of certain proteins that interfere with the binding of thyroid hormones to thyroid receptors, further impeding their activity. Finally, iron deficiency can lead to oxidative stress and inflammation, which in turn can affect the functioning of thyroid receptors. These mechanisms collectively contribute to the impaired thyroid receptor activity observed in individuals with iron deficiency.

iron deficiency anemia and thyroid

#4- Iodine Usage

Low Iron impacts how your thyroid uses Iodine. Iodine is one of those special ingredients your thyroid needs in order to make thyroid hormones. If you don’t have enough Iodine in your body, you won’t be able to make thyroid hormones. Studies have shown that without Iron, your body can’t use the iodine in order to make thyroid hormones. (*)

Iron deficiency anemia can impact iodine utilization within the body through several mechanisms. Firstly, iron is crucial for the functioning of enzymes involved in iodine uptake and thyroid hormone synthesis. Inadequate iron levels can disrupt these enzymatic processes, impairing the incorporation of iodine into thyroid hormones. Secondly, iron deficiency anemia can lead to a decreased expression of thyroid-specific proteins, which are essential for thyroid hormone production and utilization. This depletion further hampers iodine utilization and the synthesis of active thyroid hormones. Ultimately, impaired iodine usage in iron deficiency anemia can disrupt the normal functioning of the thyroid gland, leading to a range of symptoms and health complications.

So, what does all of this mean to You?

Let’s say you are taking thyroid medications and every time you go to the doctor you complain of fatigue, brain fog, weight gain, depression, hair loss, and constipation and your doctor just increases your thyroid medication and says come back in 6 months. You go back in 6 months, and nothing has changed. Can you see how increasing your thyroid medication doesn’t fix the Root Cause? And in fact, just leads to being overmedicated with Thyroid hormones.

iron deficiency anemia and thyroid

Here’s another problem I see every single day in my practice. Most health care providers will only check a patient’s iron levels if they find that your red blood cell count or your Hemoglobin levels are low.  This is WRONG WRONG WRONG! This is a huge problem because someone can be deficient in Iron yet have normal hemoglobin and normal red blood cell counts.

If your health care providers are only using hemoglobin and red blood cells counts to determine if you need to have your iron levels tested you can see how it’s going to be missed. This is one of reasons many hypothyroid patients are walking around feeling awful and all the doctor wants to do is increase the thyroid medications.

So, when it comes to an Iron testing, there are few tests you need above and beyond just your Iron levels. Those tests include Ferritin, TIBC, Percent saturation. Those are the major ones used to determine if a person needs iron or does not need Iron.

If you are someone with thyroid disease and you have not had recent bloodwork, I recommend this bloodwork panel that I have put together as part of my initial base line testing for prospective patients.

Optimal Iron and Ferritin Levels When You Have Hypothyroidism

As far as Optimal levels go.

  • Serum Iron levels (iron levels in blood) should optimally be between 85-130 (ug/dL)
  • Ferritin 80-100 (ng/mL) (iron levels stored in liver)
  • Iron saturation 35-40% expressed as a percentage
  • TIBC- middle of the reference range (ug/dL).
    • When levels start getting above 350- I start thinking early iron deficiency.

You may find that your labs are considered “normal” but they may not be optimal. As a thyroid patient you really need these results in the “optimal” range otherwise you may not feel improvement.

How To address Iron deficiency When You have thyroid disease.

To address iron deficiency anemia and optimize iodine usage, several strategies can be employed. Firstly, focusing on a balanced and nutritious diet is essential. Iron-rich foods such as red meat, poultry, seafood, legumes, and leafy green vegetables should be incorporated into daily meals with an emphasis on red meat. Additionally, consuming iodine-rich foods like

Seaweed (nori, kelp, kombu, wakame), Fish, shellfish (cod, canned tuna, oysters, shrimp), Dairy (milk, cheese, yogurt) Eggs, Beef liver can help ensure sufficient iodine intake.  Also it’s important to work and discover the Root Cause of Iron deficiency anemia. This is where working with a Certified Functional Medicine Practitioner is essential.

Iron Supplementation is necessary and should be considered when iron deficiency anemia exists, but it should only be done under the supervision of a healthcare professional/Functional medicine practitioner to prevent adverse effects and to monitor changes in iron levels.

Dr Hagmeyer Explains The Thyroid Connection To Depression

  1. Surks, MI, 1969, ‘Effects of thyrotropin and thyroidal iodine metabolism during hypoxia’ American Journal of Physiology, vol.216, pp. 436–439
  2. Galton, VA, 1972, ‘Some effects of altitude on thyroid function’. Endocrinology, vol.91, pp.1393–1403.
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