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Iron Deficiency Anemia and Thyroid Health

Published June 29 2015

Iron is one of the most commonly deficient minerals seen in people with thyroid and autoimmune thyroid conditions.  It’s surprising that many medical doctors don’t recommend an iron panel to their patients, as I frequently consult with patients who haven’t had an iron panel ordered from their primary care physician in many years, and sometimes I’ll speak with someone who claims they never had an iron panel.  It’s even more surprising when someone is experiencing symptoms such extreme fatigue, yet an iron panel wasn’t conducted.  In this article I’ll discuss iron deficiency anemia, including some of the common causes, how it can impact thyroid health, and what can be done to correct this problem.

First of all, even though I’m going to talk about iron deficiency anemia, it’s important to understand that one can have an iron deficiency without having anemia, and one can have anemia without having an iron deficiency.  To better understand this let’s discuss what happens when someone has anemia.  Anemia results when the body doesn’t produce enough red blood cells or hemoglobin.  Although many medical doctors don’t perform an iron panel, most routinely order complete blood counts to look at the red blood cells, hemoglobin, and hematocrit.  When someone has anemia one or more of these values are depressed.  Hemoglobin is an iron-rich protein which gives blood its red color, and so when iron is low, typically hemoglobin is low, along with the red blood cell count and hematocrit.  But this isn’t always the case, and so just because all three of these are normal doesn’t mean you can’t have an iron deficiency.

While a complete blood count is commonly recommended by primary care physicians when someone has a routine physical examination, in my opinion an iron panel should also be ordered.  If someone has a normal iron panel but has depressed red blood cells, hemoglobin, and/or hematocrit, then other potential causes of the anemia should be investigated.  On the other hand, if someone has an iron deficiency, regardless of whether or not they have anemia, the cause of the deficiency should be addressed.

The Components of An Iron Panel

What I’d like to do next is discuss the components of an iron panel.  The reason I want to cover this is because for those medical doctors who actually do testing to determine if a patient of theirs has an iron deficiency, many will just order a serum iron test and/or ferritin.  But after reading this you will hopefully understand why it’s necessary to obtain a complete iron panel.

Serum Iron.  This measures the amount of iron in the blood.  The average reference range is 60-170 mcg/dL, although I usually like to see this to be at least 90 to 100.

Ferritin.  Ferritin is a protein that stores iron, and a low ferritin is usually the first sign of an iron deficiency.  As a result, someone can have a normal serum iron, but if they have a low or depressed ferritin then this is indicative of an iron deficiency.  The normal reference range used by most labs is between 12-150 ng/mL.  However, when going through my masters in nutrition course I was taught that it should be at least 40 to 45, and some sources claim it should be between 70 and 90.  However, one important thing to keep in mind is that inflammation can raise the ferritin levels, which is why you can’t rely on this test alone.

Iron Saturation.  This is also referred to as tranferrin saturation or % saturation.  Iron saturation tells us how much serum iron is actually bound to a protein called transferrin.  For example, if someone has a value of 20% then this means that 20% of the iron-binding sites of transferrin are being occupied by iron.  A low value is common in an iron deficiency.  The normal reference range is between 15 to 50%, although ideally you want this to be around 30 to 35%.

Total iron binding capacity (TIBC). When iron moves through the blood it is attached to transferrin.  TIBC measures how well transferrin can carry iron in the blood.  A high TIBC means that the iron stores are low.  The lab reference range is usually between 240-450 mcg/dL.

When Is Someone Considered To Be Iron Deficient?

Most medical doctors will consider someone to be iron deficient if they fall outside of the lab reference range.  So for example, if a patient has a serum iron of 65 mcg/dL, a ferritin of 15 ng/mL, and an iron saturation of 18% they would be labeled as normal by most medical doctors.  But just as is the case with most other blood tests, there is a difference between the “lab” reference range and the “functional” reference range.  So as I mentioned earlier, if ferritin is on the low side but is still within the normal lab reference range, you need to suspect an iron deficiency.  This is especially true if the person has a low iron saturation, serum iron, and/or high TIBC.

What Are Common Causes of An Iron Deficiency?

There are three main reasons why someone becomes deficient in iron.  One reason is due to blood loss, and this is why some doctors will refer the patient with iron deficiency anemia to a gastroenterologist in order to rule out gastrointestinal bleeding.  Typically they will start with a fecal occult blood test, although a heme porphyrin test might provide a better option since it is sensitive for both proximal and distal sources of occult gastrointestinal bleeding (1) [1].  Esophagogastroduodenoscopy (EGD) and colonoscopy will find the bleeding source in 48 to 71 percent of patients (2) [2]. In patients with recurrent bleeding, repeat EGD and colonoscopy may find missed lesions in 35 percent of those who had negative initial findings (2) [2]. If a cause is not found after EGD and colonoscopy have been performed, capsule endoscopy has a diagnostic yield of 61 to 74 percent (2) [2].

A second reason for an iron deficiency is due to iron malabsorption.  This can be caused by numerous factors.  For example, in the past I have spoken about H. Pylori, which is a common infection in autoimmune thyroid conditions (3) [3] (4) [4].  Numerous studies have shown that H. Pylori infection can cause iron deficiency (5) [5] (6) [6] (7) [7], and eradication of H. Pylori can improve serum levels of iron (8) [8].  Another study concluded that malabsorption of iron is a complication of giardiasis (9) [9].  Another study showed that children with HIV infection have a higher prevalence of iron deficiency and intestinal malabsorption (10) [10].

There can be other reasons for iron malabsorption besides having an infection.  Inflammatory bowel disease can cause iron deficiency anemia (11) [11] (12) [12] (13) [13].  Celiac disease is another potential cause of iron deficiency anemia (14) [14] (15) [15].  In some instances small intestinal bacterial overgrowth (SIBO) can cause an iron deficiency (16) [16] (17) [17].  Even exposure to glyphosate can lead to the chelation of minerals such as iron, thus leading to an iron deficiency (18) [18].  Glyphosate is the active ingredient in the herbicide Roundup, and I discussed this more in an article entitled “Does Glyphosate Have A Negative Effect On Thyroid Health? [19]

A third common reason for an iron deficiency relates to low dietary intake of iron.  Iron is found in two different forms.  Heme iron is found in foods such as meat, poultry, and fish.  It is more absorbable than nonheme iron, which is found in plant based foods (19) [20] (20) [21].  As a result, vegetarians and vegans are more likely to develop an iron deficiency than those who eat meat.  However, dietary intake of heme iron, mostly in the form of red meat, can potentially increase the risk of cardiovascular disease, colon cancer, and gallbladder problems (21) [22] (22) [23] (23) [24].  Just keep in mind that these studies don’t consider the quality of the meat used, which very well might also be a factor in the development of chronic health conditions.

How Does Iron Deficiency Anemia Relate To Thyroid Health?

There are numerous minerals important for normal thyroid hormone metabolism.  Iodine and selenium are two of the more well known minerals involved in the formation of thyroid hormone.  However, iron deficiency impairs thyroid hormone synthesis by reducing activity of heme-dependent thyroid peroxidase (24) [25] (25) [26].  This of course isn’t to suggest that most cases of hypothyroidism are due to an iron deficiency, but a severe iron deficiency can be a factor.  So for example, if someone with Hashimoto’s Thyroiditis has depressed thyroid hormone levels, and also has iron deficiency anemia, while the damage to the thyroid gland by the immune system very well might be the primary reason for the low thyroid hormone levels, it is possible that the low iron levels are also a factor.

While an iron deficiency can directly affect the thyroid hormone levels, other factors which can cause an autoimmune thyroid condition can cause can iron deficiency.  I spoke about this earlier, as having an infection such as H. Pylori can not only trigger thyroid autoimmunity, but also can decrease the absorption of iron.  Other infections which can lead to the development of an autoimmune thyroid condition can also lead to iron deficiency anemia.  This is one of the main reasons why I recommend for everyone with a thyroid or autoimmune thyroid condition to obtain a complete iron panel.

What Should Be Done To Address An Iron Deficiency?

When it is determined that someone has an iron deficiency, many healthcare professionals will recommend for the patient to take iron supplements.  Although it might be necessary for someone with iron deficiency anemia to supplement with iron and/or increase their consumption of iron-rich foods, this of course doesn’t do anything for the cause of the iron deficiency.  It’s important to try to determine the cause of the low iron levels so that it can be addressed.  For example, if someone has an infection such as SIBO or H. Pylori that is responsible for the iron deficiency then of course these need to be addressed.  Plus, such infections will usually affect the absorption of other vitamins and minerals as well.  If someone has low iron levels due to a heavy menstrual flow then it’s a good idea to be aware of this as well.

Sometimes taking a thorough case history will be sufficient to determine the cause of the iron deficiency.  However, this isn’t always the case.  For example, just because someone has a heavy menstrual flow doesn’t mean they can’t also have gastrointestinal issues which are affecting the absorption of iron.  So it is very possible for someone to have more than one factor which is causing the iron deficiency.  Probably the most important factor is to make sure the person has a healthy gut.

In summary, even though many people have an iron deficiency, many medical doctors don’t routinely order iron panels.  Plus, many who do will only order a serum iron or ferritin, but it is a good idea to order a complete iron panel consisting of serum iron, ferritin, iron saturation, and TIBC.  In addition, one can’t always rely on the lab reference range to determine if someone has a deficiency.  Three main reasons why someone becomes deficient in iron is blood loss, while malabsorption of iron is another common cause.  And of course dietary intake is also a factor.  An iron deficiency can lead to a decrease in thyroid hormone levels.  And while taking an iron supplement might be necessary, it is important to determine the cause of the iron deficiency.