When is the last time you had your iron status checked? Not just serum iron levels, but hemoglobin, total iron-binding capacity (TIBC) and serum ferritin, a measure of iron stores? Knowing your complete iron status is important if you have low body temperature or low thyroid function, especially if you also are often tired, achey, out of breath, have heart palpitations or feel out of breath. These are symptoms of both thyroid malfunction and iron deficiency, and the two together just make things worse.
Here’s how iron and your thyroid interact: If the thyroid gland runs low on iron, the chemical reactions that produce thyroid hormone cannot proceed normally. Iron deficiency impairs thyroid hormone synthesis by reducing activity of heme-dependent thyroid peroxidase by 30 to 50% depending on the severity of the iron deficiency. This iron-dependent enzyme uses iodine ions and hydrogen peroxide to generate iodine, which plays a central role in the production of thyroid hormones. So you need good levels of both iodine and iron (and selenium) for your body to be able to produce adequate amounts of thyroid hormoness. In fact, research shows that people with low thyroid function respond best when they get both iodine and iron.
Women are especially likely to develop iron deficiency, because during their child-bearing years, women require more than twice as much iron as men. Doctors don’t routinely check iron status in people with low thyroid function, because it is commonly assumed that if red blood cell quantity and quality (hemoglobin level) are normal, then iron status is normal. That is not always the case.
Doctors also sometimes treat iron deficiency inadequately. They will prescribe iron supplementation until serum iron levels return to normal, but not long enough for ferritin (storage iron) to be replenished, which takes longer. Treatment may have to continue for some time after serum iron levels have returned to normal to get ferritin stores back to normal. Ferritin levels are also the first to drop when iron intake is low. So to keep ferritin levels normal it’s important to either get enough iron from foods or from supplements to keep ferritin levels normal. Too much iron isn’t good, either, though, so it’s best to work with your doctor.
2. Triggiani V, Tafaro E, Giagulli VA, et al. Role of iodine, selenium and other micronutrients in thyroid function and disorders. Endocr Metab Immune Disord Drug Targets. 2009 Sep;9(3):277-94. Epub 2009 Sep 1.
4. Casgrain A, Collings R, Harvey LJ, et al. Effect of iron intake on iron status: a systematic review and meta-analysis of randomized controlled trials. Am J Clin Nutr. 2012 Oct;96(4):768-80. Epub 2012 Aug 29.