Iron Deficiency With Thyroid Disease

If you have thyroid disease and fatigue, iron deficiency could be to blame. Low iron levels can cause fatigue and hair loss in thyroid patients. This is especially true with hypothyroidism (underactive thyroid), but it can also occur with hyperthyroidism (overactive thyroid).

You might see the terms "iron deficiency," "anemia," and "iron-deficiency anemia" used to mean the same thing. But they are different:

• Anemia involves low hemoglobin (a protein in red blood cells).
• Iron deficiency involves low iron.
• Iron-deficiency anemia (IDA) involves low iron and low hemoglobin.

This article looks at iron deficiency and anemia in hypothyroidism and hyperthyroidism, symptoms to watch for, and how it's diagnosed and treated.

Anemia in Hypothyroidism

The low thyroid hormone levels of hypothyroidism suppress the activity of bone marrow, the tissue that makes red blood cells. That lowers the production of red blood cells and triggers anemia.

Research shows anemia is diagnosed in up to 60% of people with hypothyroidism. That's compared to about 7% in the general U.S. population. Persistent fatigue is a main feature of the condition.

The relationship between iron, red blood cells, and TSH may lead to hypothyroidism by interfering with the thyroid gland's normal function.

Iron Deficiency Alone

Research suggests between 30% and 50% of people on levothyroxine (a thyroid hormone replacement medication) have chronic fatigue with no evidence of anemia.

After ruling out other conditions that cause fatigue, scientists found that iron deficiency was to blame, not IDA. In most cases, the deficiencies were caused by an iron-poor diet that existed before the thyroid diagnosis.

Anemia in Hyperthyroidism

If you have hyperthyroidism, you likely have high levels of ferritin, a protein that helps your body store iron. An overactive thyroid gland produces high amounts of ferritin.

It seems logical that increasing iron storage would prevent anemia. The opposite is often true, though. High ferritin appears to trigger an inflammatory response that prevents the body from using iron normally.

This is seen most often in Graves' disease (autoimmune hyperthyroidism). Graves' is associated with IDA and low levels of several kinds of blood cells.

What Are the Symptoms of Iron Deficiency?

Symptoms of iron deficiency and thyroid disease are similar, making it hard to spot iron deficiency or IDA. 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

If your symptoms continue despite treatment for your thyroid disease, ask your doctor to check for iron deficiency or IDA.

How Is Iron Deficiency With Thyroid Disease Diagnosed?

Iron deficiency is diagnosed with a serum ferritin test. It measures the amount of iron storage in your body.

If results are low, you'll be diagnosed with iron deficiency. If they're high, it can help confirm a hyperthyroidism diagnosis. 

Serum ferritin is not a routine part of your complete blood count (CBC). Your healthcare provider will need to order it separately.

If you're paying out of pocket, the test will likely cost between $25 and $50. Results are usually back within two days (depending on your lab).

How Is Iron Deficiency With Thyroid Disease Treated?

Iron deficiency alongside hyperthyroidism usually doesn't require treatment. It typically goes away with hyperthyroidism treatment.

In other cases, treatments for iron deficiency and IDA are based on the severity of symptoms and serum ferritin test results. It may involve iron supplements and/or an iron-rich diet.

Iron Supplementation

An iron supplement is typically prescribed to treat iron deficiency in people with thyroid disease. A typical initial dose is 65 mg of elemental iron (325 mg of ferrous sulfate) given once a day.

Your healthcare provider will likely re-test your serum ferritin after 30 to 60 days of treatment. You can stay on the supplement for up to four months. The dosage is gradually decreased as levels get back to normal.

Especially if you have a largely plant-based diet, you may want to take your iron supplement with vitamin C. Many plant foods contain substances called phytates that iron absorption in the intestines.

Vitamin C may enhance iron absorption, so consuming vitamin C-rich foods, such as citrus fruits, strawberries, tomatoes, bell peppers, broccoli, brussels sprouts, and potatoes may increase iron absorption.

Other nutrients that can help iron absorption include:

• Vitamin B12 (found in meat, fish, dairy products, and eggs)
• Folic acid (found in spinach, fortified breakfast cereals, rice, asparagus, and Brussels sprouts)
• Copper (found in potatoes, mushrooms, cashews, sunflower seeds, and tofu)

Side Effects

Iron supplements can cause side effects such as:

• Constipation
• Vomiting
• Diarrhea
• Black stools

A liquid form of iron called Floradix may be easier to tolerate.

Don't take larger doses of iron than your healthcare provider prescribes. That can lead to iron toxicity, especially at dosages above 20 milligrams per kilogram of body weight per day (mg/kg/day).

What Foods Are High in Iron for Thyroid Patients?

Adding iron-rich foods to your diet can also help get enough iron into your blood. For mild iron deficiency, it may be all the treatment you need. For more extreme cases, it may be recommended along with supplements.

Iron-rich foods include: 

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

Caffeine and calcium can interfere with iron absorption and are best avoided.

Summary

IDA and iron deficiency are common in thyroid disease and can lead to fatigue. Both hypothyroidism and hyperthyroidism can cause iron deficiency and anemia. In turn, iron deficiency can also trigger hypothyroidism.

Iron deficiency/IDA symptoms are similar to those of thyroid disease, making them hard to spot. Your healthcare provider can order a blood test, called serum ferritin, to check your iron levels.

Treatment for iron deficiency includes thyroid replacement medication, iron supplements, and/or a high-iron diet. Consuming vitamin C-rich foods when taking iron may improve iron absorption.