People across the globe are exposed to heavy metals in more ways than one.
Exposure to heavy metals paves the road to the higher risk of numerous health problems that range from mild to severe.
You have probably heard or read somewhere that heavy metals can have a negative impact on our thyroid and contribute to issues such as Hashimoto’s thyroiditis.
In this article, we are going to explore the relationship between heavy metals exposure and Hashimoto’s thyroiditis; so scroll down to learn more about this important subject.
Most common heavy metals in our environment
Before we start discussing the relationship between exposure to heavy metals and Hashimoto’s thyroiditis, it is important to address common heavy metals in our environment first. The truth is that heavy metals be absorbed into our body in different ways.
For example, we can consume them through the food or being absorbed them through the skin. Working in industrial environments also exposes us to heavy metals as well as other hazardous substances. Studies show that human exposure to heavy metals has “increased dramatically due to an exponential rise of their use in various industrial, agricultural, domestic, and technological applications. Reported sources of heavy metals in the environment include geogenic, agricultural, industrial, pharmaceutical, domestic affluents, and atmospheric sources.”[i]
Despite the fact that “heavy metals are naturally occurring elements found in earth’s crust, most environmental contamination, and human exposure happen due to anthropogenic activities like smelting operations and mining, industrial production, and use, but also from domestic and agricultural usage of metals and metal-containing compounds and substances.”
The most common heavy metals to which humans are exposed in the environment are:
- Arsenic – people get exposed to this heavy metal in many ways such as working close to dangerous waste sites, drinking contaminated water, living in an area with high levels of arsenic in water, rocks and soil, eating contaminated seafood and algae, and ingesting pesticides, insecticides and herbicides
- Cadmium – main routes of exposure to this heavy metal are through inhalation, cigarette smoke, and ingestion of food. Skin absorption of cadmium is rare. Human exposure to cadmium is possible through different sources such as employment in primary metal industries, consumption of contaminated food, smoking cigarettes, working in the cadmium-contaminated workplace, emissions from industrial activities including smelting, mining, manufacturing of batteries, pigments, stabilizers and alloys
- Chromium – over 300,000 workers are exposed annually to chromium and chromium-containing compounds in their workplace. While in humans and animals, chromium is an essential element that plays a role in glucose, fat, and protein metabolism by potentiating the action of insulin. That being said, occupational exposure has been a major concern due to a high risk of chromium-induced diseases in industrial workers
- Lead – lead exposure occurs primarily through the respiratory system by inhalation of the dust particles which is contaminated or through ingestion of contaminated food, paints, and water with lead. Adults absorb around 40- 50 % of lead through drinking water. Absorption of lead is influenced by various factors, including physiological status and age . You can get exposed to lead by living in a house containing paints with high levels of lead, being in firing ranges, using kohl cosmetics, doing radiator repair, industrial construction work, or smelter operations
- Mercury – humans, are exposed to all forms of mercury through environmental pollution, accidents, dental care, food contamination, preventive medical practices, occupational operations, and industrial and agricultural operations.
Generally speaking, we are exposed to all sorts of toxins in our environment.
These toxins can harm our health in many ways and affect the way our butterfly-shaped gland functions. Types of toxins that affect the thyroid are mainly substances that mimic the structure of thyroid hormone, contain halogens, or are heavy metals. We can divide toxins that affect thyroid into four main groups based on their source.
They are industrial chemicals, pesticides and herbicides, toxins in consumer goods, and the above-mentioned heavy metals.
Heavy metals and Hashimoto’s thyroiditis
Even though exposure to heavy metals is common today and Hashimoto’s thyroiditis is a prevalent condition this particular subject is poorly studied.
New studies about the impact of heavy metals on Hashimoto’s disease are necessary so that doctors and patients could have a detailed insight into the underlying mechanisms, but also uncover more treatment options. Despite the scarcity of studies on the topic, the current evidence confirms that heavy metals do have a negative influence on patients with Hashimoto’s thyroiditis, an autoimmune condition, and the most common cause of hypothyroidism.
Hybenova et al. report that environmental factors can play a significant role in the development of autoimmune thyroiditis and other autoimmune diseases. Although the genes responsible for a metal-induced pathology are known in experimental animals, similar knowledge is lacking in humans. Metals such as mercury or nickel induced delayed-type T cell hypersensitivity or allergy, which is quite common, particularly in women.
Patients with autoimmune thyroiditis (and other autoimmune diseases) experience increased lymphocyte reactivity to inorganic mercury, nickel, and other metals compared to their healthy counterparts. Bearing in mind that heavy metals play an important role in the development of autoimmune thyroiditis the treatment of this condition could be improved if these agents are eliminated or exposure to them restricted[ii].
Studies have shown that mercury exposure is associated with higher levels of thyroid antibodies. What’s more, the reduction of thyroid antibodies has been observed after the removal of source of mercury exposure[iii]. In other words, mercury can contribute to autoimmune thyroid disorders such as Hashimoto’s thyroiditis.
That being said, the condition can improve in cases when a patient reduces exposure to sources of mercury in their environment. This is yet another piece of evidence which confirms the role of heavy metals in thyroid autoimmunity, specifically Hashimoto’s thyroiditis. Even though thyroglobulin antibody positivity alone is not a definitive diagnostic indicator of thyroid disease, these antibodies are elevated in more than 90% of patients with Hashimoto’s thyroiditis[iv].
Speaking of mercury, it is worth noting that this heavy metal tends to accumulate in the butterfly-shaped gland, thus reducing iodide uptake at the sodium/iodide symporters by binding to iodide. Exposure to mercury impairs secretion of the T4 hormone[v]. As you are already aware, low thyroid hormone levels indicate hypothyroidism, and Hashimoto’s thyroiditis is the biggest cause of this particular thyroid problem.
Mercury is not the only heavy metal that negatively affects thyroid function and contributes or aggravates Hashimoto’s thyroiditis. For example, even a small exposure to arsenic can increase TSH and Tg (thyroglobulin) levels. As a result, this can slow down thyroid function, which is a characteristic of Hashimoto’s thyroiditis.
Due to the fact that thyroglobulin is the main protein component of thyroid follicles, it could be possible that the increase in Tg is a compensatory response by the thyroid gland to elevated concentration of TSH. Additionally, arsenic can also contribute to higher TSH levels by inhibiting TPO activity, which ends up with a reduced synthesis of thyroid hormones. Moreover, exposure to arsenic has the potential to destroy thyroid hormone receptors through gene-mediated mechanisms which are vital for normal thyroid function and reduced risk of problems affecting this gland[vi].
When talking about heavy metal exposure, it’s also useful to mention aluminum, which can alter pituitary endocrine regulation of the thyroid[vii]. Exposure to this metal can decrease TSH level and indirectly alter the function of the thyroid gland by impairing the sodium-iodide symporters, a transport system which is responsible for moving iodine from the blood to our thyroid.
The truth is that, at this point, scientists do not really know why exposure to heavy metals can contribute to symptoms of Hashimoto’s thyroiditis or aggravate them and why metals can also lead to other problems affecting our thyroid. Various mechanisms could be involved. As seen above, heavy metals alter the way iodine is transported, suppress the production of hormones, and use many other mechanisms to create a domino effect that leads to autoimmunity.
After all, these metals are pathogens that our body wants to destroy. High levels of these pathogenic compounds can cause imbalance and change the way our immune system functions. As a result, the immune system can start attacking its own tissues and lead to autoimmune problems with Hashimoto’s thyroiditis being one of the most common conditions of this kind.
Am I exposed to heavy metals?
Generally speaking, all of us are exposed to heavy metals to some extent on a daily basis. In some people, exposure is higher while in others, it is not. Not every person who is exposed to some heavy metal will display health problems such as Hashimoto’s thyroiditis, and various factors play a role here including the age, overall health, family history, just to name a few. Also, the amount or severity of exposure is yet another factor involved.
If you have Hashimoto’s thyroiditis and you work or live in an environment that is known for heavy metal exposure, your doctor may suggest getting a blood test which will show the concentration of those pathogenic compounds in your blood. You can also consult your doctor beforehand, ask whether heavy metal exposure could contribute to your condition, and suggest the blood test.
But, if you don’t have Hashimoto’s thyroiditis, your doctor may still suggest a blood test for heavy metal levels during the regular checkup. This is done in cases when a person has an increased risk of developing this condition and works or lives in environments that are known for heavy metal exposure.
Yet another scenario is that a person also displays some symptoms of heavy metal toxicity. These symptoms include weakness, chills, shortness of breath, tingling in hands and feet, diarrhea, nausea, vomiting, and abdominal pain.
Do the above-mentioned symptoms seem familiar?
If so, you’re right. Some symptoms of heavy metal toxicity are similar to those of Hashimoto’s thyroiditis. As a reminder, Hashimoto’s thyroiditis is characterized by symptoms such as increased sensitivity to cold, weakness, weight gain, muscle and joint pain, digestion problems, among others.
How to tackle heavy metal exposure?
Exposure to heavy metals affects our health in many ways, and Hashimoto’s thyroiditis is one of them. Earlier in the post, we have mentioned that reducing or avoiding exposure to mercury and other heavy metals can aid management of thyroid autoimmunity. Therefore, the most important thing you can do is to try and avoid heavy metals in your environment or at least reduce your exposure to them. There are many other ways to help your body feel better, and minimize exposure to heavy metals, reduce the risk of Hashimoto’s thyroiditis-related problems. Here are a few tips that will help you out:
- Make sure you are taking optimal levels of iodine and selenium, which attenuate the toxic effects that heavy metals can have on the thyroid. Consult your doctor regarding iodine and selenium, and they will tell you whether you are taking enough or not
- Use a high-quality water filter for drinking and bathing water because tap water can be a significant source of toxins
- Try to eat organic food as much as possible because many heavy metals and other toxins get into your body through pesticides, herbicides and other similar products used for “commercial” produce
- Look for BPA-free options when buying something plastic-related including water bottles
- Enrich your diet with fruits and vegetables and other sources of vitamins and minerals because they can exhibit a protective role against pathogens
- Consume enough fiber in order to improve your digestion and allow the body to eliminate waste properly
Exposure to heavy metals is a common occurrence worldwide, but if we don’t pay attention to it, we risk developing various health problems. Heavy metals can contribute or aggravate Hashimoto’s thyroiditis, and this is the subject you should, definitely, discuss with your doctor. Try to reduce or avoid exposure to heavy metals in your environment as much as you can.
[i] Tchounwou, P. B., Yedjou, C. G., Patlolla, A. K., & Sutton, D. J. (2012). Heavy metal toxicity and the environment. Experientia supplementum (2012), 101, 133–164. doi:10.1007/978-3-7643-8340-4_6. Retrieved from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4144270/
[ii] Hybenova M, Hrda P, Prochazkova J, et al. (2010). The role of environmental factors in autoimmune thyroiditis. Neuro Endocrinology Letters, 31(3):283-9. Retrieved from: https://www.ncbi.nlm.nih.gov/pubmed/20588228
[iii] Zehra R, Fatmi SF, Carpenter DO. (2018). Pathophysiological mechanisms of mercury’s effect on thyroid gland. International Journal of Thyroid Disorders and Therapy, 1(1):1-6. Retrieved from: https://pdfs.semanticscholar.org/60e2/ac0e2c04ae2ec178378bc640a47411332442.pdf
[iv] Gallagher CM, Meliker JR. (2012). Mercury and thyroid autoantibodies in U.S. women, NHANES 2007-2008. Environment International, 40;39-43. Retrieved from: https://publichealth.stonybrookmedicine.edu/phpubfiles/Gallagher_ENVINT_thyroid_2011.pdf
[v] Nishida M, Yamamoto T, Yoshimura Y, Kawada J. (1986). Subacute toxicity of methylmercuric chloride and mercuric chloride on mouse thyroid. Journal of Pharmacobio-Dynamics, 9(4):331-8. Retrieved from: https://www.ncbi.nlm.nih.gov/pubmed/3735055
[vi] Davey, J. C., Nomikos, A. P., Wungjiranirun, M., Sherman, J. R., Ingram, L., Batki, C., … Hamilton, J. W. (2008). Arsenic as an endocrine disruptor: arsenic disrupts retinoic acid receptor-and thyroid hormone receptor-mediated gene regulation and thyroid hormone-mediated amphibian tail metamorphosis. Environmental health perspectives, 116(2), 165–172. doi:10.1289/ehp.10131. Retrieved from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2235215/
[vii] Orihuela D. (2011). Aluminum effects on thyroid gland function: iodide uptake, hormone biosynthesis, and secretion. Journal of Inorganic Biochemistry, 105(11):1464-8. Doi: 10.1016/jinorgbio.2011.08.004. Retrieved from: https://www.ncbi.nlm.nih.gov/pubmed/22099156
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