Why you need iron for your underactive thyroid

Let’s talk about iron levels today.  This little mineral plays such a big part in our lives, and I don’t think we give it enough attention.  That is, until you struggle with fatigue, hair loss and muscle weakness!  Don’t these symptoms sound familiar?  It almost sounds like the same symptoms as hypothyroidism… 

In fact, hypothyroidism can lead to anemia, often due to an iron deficiency. 

The thing is, the metabolism of your thyroid hormones and iron are interdependent.  You need a healthy level of iron.  Too little, and you can have problems, too much and it can be toxic.  So how do you know what is enough?  Well, you must get it tested.

And herein lies the problem: few doctors test for iron when a patient has an underactive thyroid.  Or, doctors may test for it (often upon a patient’s insistence) and then tell them their levels are normal.  It’s within the lab’s reference range, so it must be normal.  But if you have been with me for a while, you will know I don’t like “normal”.  

“Normal is a setting on a washing machine.”  I read that somewhere.  If it weren’t so sad, I would have laughed.  But this is no laughing matter.  

The link between your thyroid and iron

  1. First, did you know that iron is an important element that your thyroid gland needs to make thyroid hormones?  The enzyme TPO (thyroid peroxidase) needs iron to help with thyroid hormone production (1).
  2. If you don’t have enough iron in your diet (low ferritin levels, which is the storage form of iron), it can decrease your circulating levels of Free T4 and Free T3, while TSH remains relatively unchanged (2).  This is one reason why TSH testing is not enough.  In fact, the study stated that individuals with ferritin levels below 30 mcg are at higher risk of hypothyroxinemia (low Free T4) and hypotriiodothyroninemia (low Free T3).   
  3. There was also another study that found that hypothyroidism can lead to anemia, often due to iron deficiency (3).  
  4. Hypothyroidism can also cause lower stomach acid production, which in turn creates a problem with protein digestion.  So you may struggle with digesting protein, which can lead to low iron levels. 
  5. Certain medications, like PPI’s and oral contraceptives, may also inhibited your ability to absorb iron.  

This means that if you’re managing hypothyroidism, keeping an eye on your iron levels is just as important as monitoring your thyroid hormones.

Two types of iron deficiency

Low iron levels can cause many symptoms.  But there are two important terms we need to understand:  non-anemic iron deficiency and iron deficiency anemia (IDA).

Non-anemic iron deficiency, sometimes referred to as “iron depletion” or “latent iron deficiency,” occurs when there is a reduced amount of total body iron without a corresponding drop in hemoglobin levels. This means that while your body may not have enough iron, it hasn’t yet reached the point where it affects red blood cell production significantly enough to cause anemia.

Symptoms of non-anemic iron deficiency may include 

  • fatigue, 
  • poor memory and attention
  • headaches
  • brittle nails
  • slow wound healing
  • restless legs syndrome.

Iron deficiency anemia occurs when iron levels drop so low that the body cannot produce enough healthy red blood cells. This results in a significant decrease in hemoglobin concentration, leading to the classic symptoms of anemia:

  •  fatigue,
  • weakness,
  • shortness of breath, andpale skin.

It may not seem important to know the difference.  But it is.  Often, non-anemic iron deficiency may occur before any noticeable symptoms of anemia!

Therefore, if you suspect you are iron-deficient, it is important to have it tested. 

Getting tested

Iron is the one element you should get tested, especially if you have hypothyroidism or Hashimoto’s.  

Here are the tests I recommend:

  • CBC (complete blood count)
  • Iron Panel
  • Ferritin levels

Your entire supply of red blood cells are completely replaced i about 4 months.  So if you are struggling with symptoms and suspect that iron deficiency is a problem and you haven’t had your blood tested in the last 4 months, speak with your doctor to have it tested.

References:

  1. Relationship between iron metabolism and thyroid hormone profile in hypothyroidism. https://www.msjonline.org/index.php/ijrms/article/view/9269
  2. Iron deficiency is associated with Hypothyroxinemia and Hypotriiodothyroninemia in the Spanish general adult population: Di@bet.es study. https://pmc.ncbi.nlm.nih.gov/articles/PMC5919900/
  3. Iron Status, Thyroid Dysfunction, and Iron Deficiency Anemia: A Two-Sample Mendelian Randomization Study. https://pubmed.ncbi.nlm.nih.gov/38857589/

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