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Uncovering Iron Deficiency in Thyroid Disease and Why It Matters

Iron Deficiency and Thyroid Function

If you, or someone you know, are struggling with a thyroid condition you may be wondering why hormone medications aren’t providing the expected relief. Experiencing the seemingly unrelated symptoms that come with thyroid disorders often leaves a person with no hope for answers and little support from their doctor. Should this sound familiar; it may be time to check iron levels, as a deficiency may be an underlying issue.

Thyroid patients have a high prevalence of iron deficiency, yet its significance is often underestimated in the medical community. Clinicians tend to ignore iron unless levels have reached the final stage of deficiency known as anemia. The thyroid is especially sensitive to iron such that insufficiency can be a hindrance to even the most optimal hormone therapy. In some cases improving iron status is all that’s required to reverse a thyroid condition. This is good news as it offers another avenue for a struggling patient to explore. Recognizing factors that may be contributing to a deficiency, along with ways to test and correct it, are all boxes to check off on the journey towards better health. Finally, when it comes to nutrient deficiencies, no discussion would be complete without acknowledging the impact of medications.

Causes of Low Iron and Medications

Though it would be logical to think low iron means you aren’t getting enough in your diet; when it comes to the human body, things are rarely that simple. With hypothyroidism there are numerous interferences that can result in reduced iron levels, including: low stomach acid, gluten sensitivity, chronic inflammation, menstruation, poor diet and food allergies. Medications are also important since they are commonly disregarded contributors and are so frequently administered. The information list below is provided in order to raise awareness of how medications may be part of the combination of factors leading to deficiency.

Drugs known to deplete iron:

  • Aspirin
  • Antibiotics: gentamicin, neomycin, tobramycin, & ciprofloxiacin “cipro”.
  • Antacids
  • Aluminum, calcium, and magnesium-containing preparations
  • Cholesterol lowering medications: Questran & Colestid
  • NSAIDS: diclofenac, diflunisal, etodolac, fenoprofen, ibuprofen, naproxen
  • Ulcer medications

The Role of Iron in Thyroid Functioning:

Conventional hormone treatments for hypothyroid and autoimmune Hashimoto’s thyroiditis are levothyroxine (generic) or Synthroid (name brand). Unfortunately, this treatment option is far from optimal and are rarely effective. One reason for this is the hormone cannot convert properly without essential minerals supporting their function. Selenium, iodine, zinc and iron are all necessary to synthesize and metabolize the thyroid hormones. Levothyroxine increases T4 (thyroxine) levels, however the body relies on iron, selenium and zinc to convert T4 to the active hormone T3 (triiodothyronine). The minerals themselves also rely on each other. For instance, iodine requires iron in order to be fully utilized. Considering iodine is the chief component of thyroid hormones, its utility is critical. Current research identifies some of iron’s other roles and patterns as follows:

  • Iron (in the heme form) is necessary for thyroid hormone production.
  • Iron is necessary to convert T4 to T3; T3 is the active form.
  • Iron status (ferritin) inversely correlates with TSH.
  • Iron is critical for thyroid peroxidase activity (TPO).

Identifying Symptoms

Since low iron impairs thyroid function, it makes sense that hypothyroid-like symptoms are common characteristics, easily masking the problem. The relationship is so notable that chronic deficiency may be a sign of poor thyroid function. In fact, some experts suggest thyroid testing in cases where low iron is chronic. The list of symptoms below illustrates the similarities:

Symptoms of low iron:

  • Hair loss or lack of growth
  • Chronic fatigue and low energy
  • Exercise intolerance and fatigue (less oxygen to cells)
  • Frequent illness
  • Anxiety
  • Increased heart rate
  • Difficulty staying warm; cold extremities
  • Digestive issues, i.e. gas, bloating, low stomach acid
  • Low stomach acid impeding B12, folate and vitamin D deficiencies

Testing For Deficiency

Thyroid diseases are prime examples of modern medicine falling short in a situation where correcting a nutrient deficiency might make all the difference for the patient. Iron levels are overlooked unless bloodwork indicates anemia, which is a descriptive term for having a reduced size or number of red blood cells (RBC). Having reduced RBC capacity means less oxygen is being transported to the brain, muscles and heart. Many of the deficiency symptoms listed above are consequences of this; yet, once again things aren’t cut and dry. If a person is deficient but not anemic, RBC and blood serum iron levels could appear normal even when levels are low. In cases of thyroid diseases where the effects of deficiency are magnified it is important to address the deficiency before it leads to anemia. True iron status can be identified with standard blood tests including a complete blood count and a full iron panel, which includes the following:

  • Ferritin
  • Serum Iron
  • TIBC (Total Iron Binding Capacity)
  • Transferrin (%) Saturation

Ferritin levels are considered the most sensitive test for iron status with optimal levels >50 ng/ml, though accurate assessment is only done in context of the complete panel. To do a comprehensive the assessment it would be prudent to also include homocysteine, B12 and methylmalonic acid, which are associated with B12 status. Vitamin B12 is closely associated with thyroid disease, iron status, as well as drug -induced deficiencies.

How to Boost Iron Levels

It’s important to remember with iron and the other thyroid supporting micronutrients, there is a narrow window between too little and too much. As a result it is generally advised levels be monitored when supplementing. Working with a knowledgeable professional is recommended for addressing the interferences previously mentioned, testing for deficiency as well as supplementation. As part of this process, here are some things you can do to boost your levels:

  • Avoid having iron within four hours of thyroid medications.
  • Taking vitamin C at the same time can enhance iron supplementation.
  • Iron rich foods include: oysters, fortified cereals, beef liver, lentils, spinach, tofu, white beans, and dark chocolate.
  • Recheck iron panel after 4-6 weeks of supplementation.


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