Iron Deficiency With Thyroid Disease

Addressing low levels may help beat fatigue and other symptoms

Red meat is one of the richest food-based sources of iron.
Justin Sullivan/Getty Images News

If you're one of the many people with a thyroid problem who suffers from fatigue, iron deficiency could very well be to blame. This is especially true in people with hypothyroidism (low thyroid function) but can also occur with hyperthyroidism (overactive thyroid function).

A simple blood test can usually diagnose the condition. Iron supplementation and dietary changes, along with the proper management of your thyroid disease, is usually all that is needed to resolve related symptoms.

With Hypothyroidism

With hypothyroidism, the reduced supply of thyroid hormones suppresses bone marrow activity, diminishing the production of red blood cells and triggering the onset of anemia. According to a 2013 study published in Endocrine Journal, as many as 43 percent of people with overt (symptomatic) hypothyroidism have anemia compared to 29 percent in the general population. Unremitting fatigue is one of the central features of anemia.

Interestingly, research also suggests that iron deficiency can contribute to the development of hypothyroidism. This is because iron is central to the production of both red blood cells and thyroid stimulating hormone (TSH). In fact, the lack of iron can cause a specific form of anemia known as iron deficiency anemia.

The interrelationship between iron, red blood cells, and TSH can contribute to hypothyroidism by interfering with the normal function of the thyroid gland.

Iron Deficiency Without Anemia

While it had been long presumed that hormone replacement drugs like levothyroxine could alleviate anemia by restoring normal TSH levels, research presented at the 2015 International Thyroid Congress suggested that may not be the case.

According to the research, between 30 percent and 50 percent of people on levothyroxine therapy experience ongoing fatigue despite treatment and with no evidence of anemia.

After excluding diabetes, B12-vitamin deficiency, celiac disease, hypercalcemia, and vitamin D deficiency as causes, the scientists finally concluded that iron deficiency, irrespective of anemia, was to blame. In most cases, the deficiencies were traced to inadequate iron intake originating before the diagnosis.

With Hyperthyroidism

Ferritin, a protein responsible for storing iron in the body, is characteristically elevated in people with hyperthyroidism. When the thyroid gland is overstimulated by excessive amounts of TSH, it will produce large quantities of ferritin.

While it would be fair to assume that the increased storage of iron would prevent anemia, the opposite is often true. In fact, it appears that the hyperproduction of ferritin triggers an inflammatory response that actually suppresses the metabolism of iron.

This is most especially seen with Graves' disease, a cause of hyperthyroidism associated with anemia, neutropenia (low neutrophil), thrombocytopenia (low platelets), and either high or low white blood cell counts.

Symptoms of Iron Deficiency

Iron deficiency manifests with a significant drop in red blood cells. Red blood cells, along with the carrier molecule hemoglobin, are responsible for distributing oxygen throughout the body and transporting carbon dioxide back to the lungs for removal.

Symptoms of iron deficiency can mirror or coincide with those in thyroid disease. They include:

  • Persistent fatigue
  • Pale skin
  • Shortness of breath
  • Headaches
  • Dizziness
  • Heart palpitations
  • Dry skin
  • Brittle hair and hair loss
  • Swelling or soreness of the tongue or mouth
  • Restless legs
  • Brittle or ridged nails

As many with thyroid disease are already very familiar with the symptoms on this list, low iron levels can easily get overlooked, as patients may chalk what they are experiencing up to their condition rather than some other cause.

Diagnosis

The serum ferritin test measures the amount of iron storage in the body. The normal range in men is 20 to 500 nanograms per milliliter (ng/mL) and 20 to 200 ng/mL in women. Unlike other lab tests, you do not need to fast prior to the blood draw.

If results are below the reference range, iron deficiency can be definitively diagnosed. If the results are high, it can help cement a diagnosis for hyperthyroidism

While hyperthyroidism can sometimes interfere with iron metabolism, manifested by increased ferritin levels, this issue resolves when the hyperthyroidism is adequately treated and does not require any additional evaluation or treatment. Serum ferritin is not a routine part of your complete blood count (CBC) and needs to be requested by your doctor. It is not a complicated test and tends to cost between $25 and $50 if you're paying out of pocket.

To get an accurate result, you may be asked to fast for 12 hours prior to the blood draw. Test results are usually received within two days depending on your lab.

Treatment

The treatment of iron deficiency is based largely on the severity of symptoms and the results of the serum ferritin test. It may involve oral supplementation and/or a diet high in iron.

Iron Supplementation

A twice-daily iron supplement is typically prescribed to treat iron deficiency in people with thyroid disease. For mild anemia, the recommended dosage is 60 milligrams twice daily for a total dose of 120 milligrams.

After 30 to 60 days, a serum ferritin test should be performed to check if the iron levels have normalized. The treatment can be continued for up to four months, with the dosage gradually decreased as the levels start to normalize.

If you are on hormone replacement therapy, an iron supplement should be taken at least three to four hours before or after levothyroxine. Taking them together interferes with the absorption of the thyroid replacement drug.

You may want to consider taking your iron supplement with vitamin C, particularly if you are vegan or vegetarian. This is because many plant foods contain phytates that bind to iron and prevent their absorption in the intestines. Iron has an increased affinity for vitamin C and, by binding to it, can be easily absorbed, increasing the bioavailability of iron in the blood. Vitamin B-6, B-12, folic acid, and copper have a similar effect.

Iron supplements can cause side effects such as constipation, vomiting, diarrhea, or the blackening of stools in some people. A liquid iron formulation, called Floradix, may be better tolerated in those who experience stomach upset on tablets.

You should never take larger doses of iron, vitamin C, or any other mineral or vitamin beyond what is recommended by your doctor. Doing so can lead to iron toxicity, particularly at dosages greater than 20 milligrams per kilogram per day (mg/kg/day). Similarly, the overuse of vitamin C can cause diarrhea and nausea.

Dietary Iron Sources

The highest sources of iron are red meat and organ meat (such as liver and giblets). Other iron-rich foods you can add to your diet include: 

  • Pork
  • Poultry
  • Mollusks (such as oysters, mussels, clams)
  • Eggs
  • Chickpeas
  • Pumpkin seeds and sesame seeds
  • Lentils
  • Dried fruit (like raisins, apricots, and prunes)
  • Iron-fortified bread, pasta, and cereal

Two iron-rich foods—soybeans and spinach—may not be so thyroid-friendly. You should avoid the overconsumption of soy products as they can slow thyroid function. And always be sure to steam or cook spinach to avoid the development of goiters.

You should also make a point of limiting your intake of caffeine and calcium-rich foods, which may also impede the absorption of iron.

Was this page helpful?
Article Sources