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One of the most common symptoms of thyroid disease is fatigue. For people with hypothyroidism (an underactive thyroid), low thyroid hormone levels that slow the metabolism may cause fatigue. However, there is another plausible reason why people feel so exhausted in this condition—it may be due to low iron levels.
Iron is a mineral that our bodies uses for many functions, including helping our muscles store and use oxygen. If you have too little iron, you may develop iron deficiency.
Iron deficiency is where your body does not have an adequate supply of iron stores. Sometimes, this can lead to anemia, where your blood lacks a sufficient amount of healthy red blood cells (RBCs). We need healthy RBCs to transport oxygen to all of the cells in the body. Iron is necessary for oxygen to bind to red blood cells.
The most apparent cause of iron deficiency is blood loss. Women are more likely to have iron deficiency than men because of menstrual bleeding. Still, people of all ages and stages can have iron deficiency. For example, gastrointestinal bleeding is the most common cause of iron deficiency in men and postmenopausal women. Other instances where iron deficiency may occur include pregnancy, postpartum, breastfeeding, infancy, and adolescence.
The most common symptom of iron deficiency is fatigue. This response is because your cells do not get enough oxygen to support their necessary functions.
Other symptoms of iron deficiency include:
- Pale skin
- Headaches, lightheadedness, and dizziness
- Tongue inflammation and soreness
- Cold extremities
- Poor appetite
- Unusual cravings for items like ice, dirt, or starch
Hypothyroidism can cause different types of anemia. Thyroid hormones affect the formation of red blood cells by directly or indirectly stimulating erythropoietin, a hormone produced by the kidneys that makes RBCs. Reduced availability of thyroid hormones also suppresses bone marrow activity, which is where RBCs form.
Over 40 percent of people with overt hypothyroidism have anemia. Compared to the general population, where 29 percent have some form of anemia, there is a correlation between hypothyroidism and anemia.
Intriguingly, research from 2017 suggests that iron deficiency may also lead to hypothyroidism. Iron plays an important role in thyroid hormone production, along with other minerals like iodine, selenium, and zinc.
Thus, some interrelationship between thyroid hormones, iron, and RBCs can be disrupted by either a poorly functioning thyroid or low iron stores.
An overactive thyroid may also impact iron stores. People with hyperthyroidism have elevated ferritin levels. Ferritin is a protein that stores iron in the body. Thus, hyperthyroidism can cause you to produce large amounts of ferritin. Likely one would think that would increase your iron stores. Still, it turns out that too much ferritin can cause an inflammatory response the suppresses iron metabolism. This response is commonly seen in Graves’ disease and often leads to anemia.
Suppose you have any symptoms associated with iron deficiency or have a thyroid disease. In that case, you should have your iron levels checked by a blood draw. Depending on your labs, your doctor can determine if your symptoms are related to low iron stores or if you are suffering from anemia. Your doctor will likely request a complete blood count (CBC) when you check your iron levels. If you have hyperthyroidism, you may also need to request ferritin added to your labs, as it is not always standard practice to check ferritin.
Keep in mind, normal ranges for these labs depend on whether you are male or female and your age.
You can correct an iron deficiency by either taking supplemental iron or increasing your intake of iron-rich foods. People with thyroid disease and iron deficiency usually need to take iron supplements twice daily, with a dose ranging between 60 mg to 120 mg depending on your lab results and the severity of your symptoms.
People taking thyroid hormone medication like levothyroxine need to separate when they take their thyroid medication from their iron supplement. Iron interferes with thyroid medication absorption in the gut, which can lower the thyroid hormone in your body.
Once you have been taking supplements for about two months, your doctor will likely repeat your iron labs to see if you are at a therapeutic level. To maximize iron absorption, some people take it with vitamin C, which makes it easier to absorb and boosts its bioavailability.
You can naturally boost your iron intake through your diet as well. Red meats contain the highest sources of iron (as do organ meats like liver).
Increase your iron intake by eating:
- Oysters, mollusks, and clams
- Dried fruit
- Pumpkin seeds and sesame seeds
- Iron-fortified foods
Taking too much of any vitamin or mineral can have detrimental effects on your health as well. If you need to replenish low iron stores, make sure to follow up with your doctor to check your labs and ensure you are on the right treatment plan.
Work with a thyroid nutritionist to develop a customized nutrition plan:
A note from Paloma Health
Thyroid disease can affect every cell in your body, even your red blood cells. Treating your thyroid can take care of several frustrating symptoms, including chronic fatigue. Check your thyroid levels with an at-home thyroid test kit to regain control over your thyroid health and wellbeing.