Table of Contents
- 1 Iron deficiency and thyroid
- 2 Why is iron deficiency often undiagnosed?
- 3 Influence of iron on key enzyme
- 4 Iron and hyperthyroidism
- 5 Iron overload and thyroid
- 6 How much iron I need?
- 7 Conclusion
- 8 References
We have already examined how minerals affect the thyroid. In that article, we also glossed over Iron, but we did not really expand on it with detail. Let’s do that.
Iron is a mineral your body needs to function properly.
All cells in the body contain iron, but it is most prevalent in red blood cells which transport oxygen from the lungs to your organs and tissues.
The mineral creates energy from nutrients and contributes to the transmission of nerve impulses (the signals which coordinate actions to different parts of the body).
Since all cells contain iron and it is of huge importance for our health, we have to wonder about its relationship with the thyroid gland. Does this mineral play any role in the functioning of the gland and vice versa?
Let’s find out.
Iron deficiency and thyroid
Nutritional deficiencies occur when the body doesn’t absorb or obtain from the diet the necessary amount of some particular nutrient. Mineral and/or vitamin deficiency, such as iron, can often be the cause.
According to the World Health Organization (WHO) iron deficiency is the most prevalent nutritional disorder in the world. It is also the only nutritional disorder that is significantly widespread in industrialized countries[i] (most nutritional deficiencies occur in underdeveloped nations.)
Evidence shows that an average of 5.6% of the US population meets the criteria for anemia (primarily caused by iron deficiency) and more than 1.5% of the population has severe anemia[ii].
The truth is that iron deficiency causes a number of negative health effects and they also extend to the functioning of thyroid gland.
For many years scientists have been investigating the relationship between iron deficiency and thyroid.
A study from the Journal of Nutrition used iron-deficient anemic rats and found they had lower basal values of thyroid-stimulating hormone (TSH) and blunted TSH responses to intravenous thyrotropin-releasing hormone (TRH) injection at three different dosages.
Anemic and iron-deficient animals also exhibited a major decrease in plasma T3 hormone turnover and significantly lower T4 than compared to rats that were not iron-deficient.
Researchers from the Pennsylvania State University explained that decreased rates of T3 could be associated with the reduction in deiodinase activity (an enzyme involved in the activation/deactivation of thyroid hormones) and decreased peripheral formation of the T3 hormone.
They concluded the study confirming that abnormal thyroid state could be partially responsible for disrupted thermogenesis in iron-deficient anemia[iii].
Iron deficiency has a negative impact on the functioning of thyroid gland and the above-mentioned research wasn’t the only one to record it.
A study whose findings were published in the Asia Pacific Journal of Clinical Nutrition examined the influence of iron deficiency on thyroid metabolism. Scientists discovered the notable correlation between T4 and ferritin (a protein that body binds to iron) and between TSH and ferritin. Iron-deficient participants with low ferritin levels had a relatively higher ratio of thyroid hormones T3 and T4.
These findings led to a conclusion that severity of iron deficiency plays a role in thyroid hormone status[iv].
Iron deficiency makes hypothyroidism worse
Hypothyroidism and iron deficiency often go hand in hand primarily because the mineral is required for the adequate function of the butterfly-shaped gland.
A study by Zimmermann MB found that iron deficiency disrupts thyroid hormone synthesis by reducing the activity of heme-dependent thyroid peroxidase. While iron deficiency anemia impairs the supplementation improves the efficacy of iodine supplementation[v].
As seen above, not only is this mineral important to produce thyroid hormone, but low levels of iron are closely linked with decreased concentration of T3.
What does this mean for hypothyroid patients?
Basically, low level of irons contributes to the decreased production of T3 and result in aggravated symptoms of hypothyroidism.
This could also explain why some patients don’t experience relief in symptoms even though they take medications as recommended.
What’s more, studies show that a combination of iron supplementation and levothyroxine proves to be effective for hypothyroid patients and helps them regulate thyroid hormone levels and tackle iron deficiency at the same time[vi].
If your body doesn’t get sufficient amount of iron, you are less likely to utilize iodine if you’re supplementing with it.
Since iodine is crucial for hypothyroid patients, the body’s inability to use it is a significant problem that makes the condition worse.
As a result, some iodine patients may believe taking a supplement isn’t working for them when in fact the body is unable to use it due to iron deficiency.
Why is iron deficiency often undiagnosed?
Iron deficiency is the most prevalent nutritional disorder in the world, but the problem is more severe than we think.
That’s because iron deficiency is usually misdiagnosed, especially in hypothyroid patients. Symptoms of hypothyroidism and deficiency in this mineral are similar.
A hypothyroid person may exhibit some symptoms that are assigned to their condition although levels of iron in their body are very low.
For example, symptoms of iron deficiency include the following:
- Appetite problems
- Brittle nails
- Cold hands and feet
- Extreme fatigue
- Inflammation or soreness of the tongue
- Pale skin
- Shortness of breath, fast heartbeat, chest pain
Let’s take a look at symptoms associated with hypothyroidism:
- Dry hair
- Elevated blood cholesterol levels
- Heavier than normal menstrual periods
- Pain and stiffness in joints
- Pale skin
- Sensitivity to the cold/cold hands and feet
As you can see, some symptoms of iron deficiency and hypothyroidism overlap. This leads us back to the ineffective iodine supplementation and lack of relief in symptoms you experience.
Since iron deficiency is often left undiagnosed, a patient doesn’t receive adequate treatment, which only turns into a bigger problem in the long run.
Influence of iron on key enzyme
The Biomedical Research published a study which found that levels of ferritin, iron decrease while those of total iron binding capacity (TIBC) increase in hypothyroid patients. Metal ions, primarily iron, are important for the production of reactive hydroxy radicals which shift the balance of the body toward higher oxidative stress.
Patients with hypothyroidism experience increased oxidative stress and iron is crucial for this mechanism i.e. it plays the role in increase or decrease of oxidative stress in your body.
Iron is also required for generation of reactive oxygen species. High TSH levels reduce the number of inflammatory cytokines, but they also decrease the concentration of antioxidants. This is important because of ferritin functions as an antioxidant too.
The research also revealed that the key enzyme in thyroid hormone biosynthesis, thyroperoxidase, is iron-dependent.
Therefore, iron deficiency could pose as an underlying cause in hypothyroidism development. These findings only go to show that relationship between iron and thyroid function is deeper than previously thought.
It is also important to mention that iron plays a significant role in the mechanism that transports thyroid hormone into the cells. Insufficient levels of iron contribute to pooling of thyroid hormone and create a metabolically hypothyroid image even if a patient has healthy levels of T3[vii].
Iron and hyperthyroidism
Although the relationship between iron and hypothyroidism is well-studied, evidence about its impact on hyperthyroidism is still limited. A group of scientists from Turkey carried out a study the analyze the impact of iron supplementation on the parameters of oxidative stress in hyperthyroidism-induced rats.
Results showed that supplementation in this mineral attenuated the hyperthyroid state, but it also lowered ferritin levels, which is an indicator of thyroid hormone action.
Iron supplementation was linked with a decrease in the risk of oxidative stress in hyperthyroid animals, not increase as scientists expected[viii].
Iron overload and thyroid
Even though iron deficiency is common, it is also possible to have too much iron in the body. Although iron overload is rare, it is important to address its impact on your gland. Certain health conditions, like thalassemia or hemochromatosis, can lead to the accumulation of excessive levels of iron in the tissues.
These particular disorders cause iron overload by enhancing absorption of the mineral from the intestine. While hemochromatosis is an inherited disorder, patients start experiencing symptoms in their 50s.
Evidence shows that increased iron storage or deposition has a harmful impact on the endocrine glands[ix].
The pituitary gland is more sensitive to iron toxicity than other organs in the body and is more damaged by the overload. That’s why it’s not uncommon for patients who suffer from these disorders to develop hypothyroidism due to iron-induced damage.
Healthy ferritin levels
As seen throughout this post, ferritin levels play a major role in the relationship between iron and thyroid functioning. It is highly recommended to measure ferritin levels, particularly if you already have some thyroid disorder.
Ferritin levels are measured through a blood test. Typical ranges that indicate healthy ferritin levels include 20 to 500 nanograms per milliliter for men and 20 to 200 nanograms per milliliter for women. Bear in mind that not all laboratories have the same results for ferritin levels. Although these are standard ranges, some labs may have different values. That’s why you should consult a doctor whether ferritin levels in your blood are normal, high, or too low.
How much iron I need?
Sufficient consumption of iron is vital for good health and wellbeing, including thyroid gland function. Fortunately, you can obtain required daily values through your diet alone.
How much iron you need on a daily basis?
National Institutes of Health recommend the following daily intake of iron[xi]:
- Birth to 6 months – 0.27 mg
- 7-12 months – 11 mg
- 1-3 years – 7 mg
- 4-8 years – 10 mg
- 9-13 years – 8 mg
- 14-18 years – 11 mg for males, 15 mg for females
- 19-50 years – 8 mg for males, 18 mg for females
- 51+ years – 8 mg
Best sources of iron
As already mentioned, we have the opportunity to get required iron levels straight from the diet. The best sources of this mineral include:
- Black beans: 1.8 mg (10% DV) per ½ cup
- Dark chocolate: 3.3 mg (19% DV) per 1 ounce
- Grass-fed beef: 4 mg (22% DV) per 214 grams strip steak
- Lentils: 3.3 mg (20.4% DV) per ½ cup
- Liver: 4.05 mg (22.5% DV) per 3 ounces
- Pistachios: 1.1 mg (6.1% DV) per 1 ounce
- Raisins: 1.1 mg (6.1% DV) per ¼ cup
- Sardines: 1.8 mg (10% DV) per ¼ cup
- Spinach (cooked): 3.2 mg (17.8% DV) per ½ cup
- Spirulina: 8 mg (44% DV) per 1 ounce
Other great sources of iron include egg yolks, poultry, oysters, chickpeas, pumpkin seeds, sesame seeds.
Iron is an essential mineral that our body needs to function properly. Levels of this mineral have a deep impact on different organs and tissues in our body including thyroid gland. Iron deficiency is very common, but often left undiagnosed, and it affects the production of thyroid hormones.
It is important for patients with thyroid disorders, or those who are at a higher risk of developing them, to test their iron levels.
[i] Micronutrient deficiencies: Iron deficiency anemia, WHO http://www.who.int/nutrition/topics/ida/en/[ii] Chi Huu Hong Le. The prevalence of anemia and moderate-severe anemia in the US population (NHANES 2003-2012). PLoS One 2016 Nov. Doi: 10.1371/journal.pone.0166635 http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0166635
[iv] Eftekhari MH, Keshavarz SA, Jalali M, et al. The relationship between iron status and thyroid hormone concentration in iron-deficient adolescent Iranian girls. Asia Pacific Journal of Clinical Nutrition 2006;15(1):50-5 https://www.ncbi.nlm.nih.gov/pubmed/16500878
[v] Zimmermann MB, Kohrle J. The impact of iron and selenium deficiencies on iodine and thyroid metabolism: biochemistry and relevance to the public health. Thyroid 2002 Oct;12(10):867-78. Doi: 10.1089/105072502761016494 https://www.ncbi.nlm.nih.gov/pubmed/12487769
[vi] Cinemre H, Bilir C, Gokosmanoglu F, et al. Hematologic effects of levothyroxine in iron-deficient subclinical hypothyroid patients: a randomized, double-blind, controlled study. Journal of Clinical Endocrinology and Metabolism 2009 Jan, vol. 94 no. 1, 151-156. Doi: 10.1210/jc.2008-1440 https://academic.oup.com/jcem/article/94/1/151/2597906/Hematologic-Effects-of-Levothyroxine-in-Iron
[vii] Dahiya K, Verma M, Dhankhar R, et al. Thyroid profile and iron metabolism: mutual relationship in hypothyroidism. Biomedical Research 2016 Apr; 27(4): 1212-1215 http://www.alliedacademies.org/articles/thyroid-profile-and-iron-metabolism-mutual-relationship-in-hypothyroidism.pdf
[viii] Seymen HO, Civelek S, Seven A, et al. Iron supplementation in experimental hyperthyroidism: effects on oxidative stress in skeletal muscle tissue. Yonsei Medical Journal 2004 Jun 30;45(3):413-8. Doi: 10.3349/ymj.2004.45.3.413 https://www.ncbi.nlm.nih.gov/pubmed/15227727
[ix] Abdulzahra MS, Al-Hakeim HK, Ridha MM. Study of the effect of iron overload on the function of endocrine glands in male thalassemia patients. Asian Journal of Transfusion Science. 2011;5(2):127-131. doi:10.4103/0973-6247.83236. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3159240/
[x] Tamagno G, de Carlo E, Murialdo G, et al. A possible link between genetic hemochromatosis and autoimmune thyroiditis. Minerva Medica 2007 Dec;98(6): 769-72. https://www.ncbi.nlm.nih.gov/pubmed/18299688
[xi] Iron, National Institutes of Health https://ods.od.nih.gov/factsheets/Iron-HealthProfessional/