Effects of Cadmium on thyroid gland
What is the connection between cadmium metal and thyroid?
Cadmium (Cd) is a silvery metal sitting next to zinc on a periodic table. The metals often appear together in nature. Unfortunately, unlike zinc, cadmium is a toxic and carcinogenic. Even though cadmium release into environment is closely controlled by government legislation, cadmium is impossible to avoid. More and more people are getting closer to reaching toxic levels, especially with increased age and those who had occupations exposing them to cadmium or exposed to cigarette smoke. Cadmium accumulates in the body and is difficult to excrete. Cadmium is found in soils (especially those industrially polluted), artists’ paints (orange, yellow and red), pigments, bake ware, nickel cadmium batteries, phosphorous fertilizers, plastics stabilizers, corrosion-resistant metal plating, metal alloys, brake lining of cars, pollution from power plants, mining and smelting and from production of some foods like margarine. Cd may be present in some plants (especially grown on soils contaminated with industrial pollution, green leafy plants tend to uptake it more easily), some organ meats (liver and kidneys), molluscs and other shellfish in some areas (as they tend to accumulate it) and large ocean fish. Some plants such as tobacco, marijuana and rice tend to uptake Cd more readily. Coffee and black tea may also contain some cadmium. Cigarettes are a significant source of cadmium exposure as lungs take up cadmium more readily than the digestive system. It is considered a substantial source of cadmium toxicity in humans. It generally doubles the cadmium intake. We also have to remember that cigarette smoke also contains other substances including thiocyanate that inhibits iodine uptake by the thyroid gland. Nicotine in cigarettes increases the synthesis of T3 from T4 in the brain, which might explain the difficulty in quitting smoking as higher T3 levels correspond to higher serotonin (feel good chemical) levels in the brain. However since cadmium is such a toxic metal, its influence on thyroid cannot be overlooked. Thyroid is one of organs that tends to accumulate cadmium.
What is the relationship between cadmium, thyroid and autoimmunity?
Cadmium and other toxins present in cigarettes interfere with thyroid gland function and thyroid hormone T4 to T3 conversion; they may cause damage to the thyroid resulting in the generation of autoantibodies. Cadmium exposure is associated with thyroid autoimmunity (both Graves’ disease and Hashimoto’s thyroiditis) in genetically predisposed people. A study of 132 pairs of twins showed that cigarette smoke exposure was connected with thyroid autoimmunity with higher rates (about 2.5X higher) for Graves’ disease than Hashimoto’s thyroiditis. It was also less significantly associated with non-autoimmune thyroid diseases (simple goiter and nodular toxic goiter) (17).
There is some suggestions in literature that Hashimoto’s thyroiditis may be triggered by cadmium especially when iodine and selenium levels are low. People with Graves’ disease may have adequate iodine levels (although not always) but are also usually low in selenium.
Graves’ disease is strongly connected to cadmium toxicity. It is especially connected to Graves’ disease with TED (eye involvement). Smoking has been connected with higher incidence of GD in females (26). It is believed that cigarette smoke may increase the risk of GD as much as two fold. Acropachy association with TED tends to represent the most severe form of autoimmune thyroid disease, with patients having very high levels of thyroid stimulating antibody. Cigarette smoking rates were found to be high in these individuals. Cd disrupts the ratio of copper and zinc which are vital for thyroid function. It contributes to copper deficiency, condition which accelerates thyroid function. Copper deficiency can occur when the body uses copper very fast (perhaps when children and teens get Graves’ disease) or when it cannot use copper efficiently and stores it in unusable form. Cadmium also interferes with zinc metabolism and competes with copper and zinc for binding on a transport protein called metallothionein. Also, in the cause of adrenal exhaustion, due to chronic stress for example, metallothonein is not produced in sufficient quantities. When this happens, copper is not metabolized properly. Copper deficiency affects the immune system and can also result in hyperactivity, high blood pressure and overuse of the sympathetic nervous system. According to Dr. Willson (9) cadmium toxicity may contribute to violent human behavior. Cd exposure may cause GABA imbalances (calming molecule in the brain). Cd also interferes with metabolism of vitamin D which is important for the balance of the immune system. It also decreases magnesium levels (common deficiency with autoimmune thyroid conditions). Cadmium can also induce iron deficiency anaemia. Cadmium damages mitochondria, organelles where energy is produced. Dysfunctional mitochondria are connected to autoimmunity. Cd toxicity has also been connected to rheumatoid arthritis and Multiple sclerosis. Cadmium may also bind to glutathione making it ineffective. Glutathione is a free radical scavenger, important for the health of the thyroid gland.
Reducing Cadmium levels may be important for some people in achieving a remission from thyroid autoimmunity.
Do some people absorb Cd more easily?
This predisposition to accumulate those specific metals might be connected to individual’s genetics. It is also relates to a poor stress management. Females tend to absorb Cd more easily due to higher levels of oestrogen hormone (necessary for ovulation and pregnancy). Oestrogen may act as an accelerator of mineral uptake into the body; it may act to enhance cadmium absorption. Women who have insufficient levels of progesterone to balance oestrogen may accumulate Cd more easily. People with low iron stores are especially vulnerable to the adverse effects of cadmium. As cadmium tends to accumulate with age (it is difficult to get rid of), it causes lowered levels of zinc which is needed for thyroid hormonal binding to their receptors. This may explain higher risks of hypothyroidism in older people, especially women. Also, older cells have a reduced capacity to produce Metallothioneins (MTs) which is are protective against Cd toxicity and proper levels of zinc and copper. Adrenals glands need to strong for sufficient production of this molecule.
Stress and cigarette smoke exposure can induce Graves’ disease as it lowers production of metallothioneins and increased Cd exposure. This trigger might be especially powerful in younger people as they tend to use copper fast. Copper deficiency accelerates thyroid function and damages the energy producing mitochondria. It was found to interfere with Coenzyme A, which helps to transport free fatty acids to mitochondria for energy production.
What Cadmium does in the body?
Cadmium tends to accumulate in the thyroid gland and therefore may cause thyroid damage due to its toxicity. It is one of the triggers for thyroid autoimmunity in individuals who are genetically predisposed to autoimmunity. In significant levels, it depletes selenium mineral which is extremely important for the health of the thyroid gland as it important for the glutathione peroxidase system which removes free radicals from the thyroid gland. In the thyroid gland, free radicals are produced continuously due to oxidation of iodine by hydrogen peroxide for the production of thyroid hormones. If free radicals are not properly controlled by glutathione peroxidase in the thyroid, they damage the thyroid cells and the lipid membranes. Cadmium toxicity increases free radicals in the body overall. Cd was shown to inhibit superoxide dismutase (copper, zinc based), two antioxidant enzymes. Cd toxicity may therefore play a role in other autoimmune disorders.
Cd was found to decrease T4 levels and increase T3 levels in a Japanese study comparing residents of the Cd-polluted Kakehashi River basin with residents of a nonpolluted area (1). Therefore Cd can induce T3 thyrotoxicosis and hyperthyroidism which was also demonstrated in animal studies (5). In people predisposed to autoimmunity, it can cause thyroid autoimmunity. High levels of cadmium exposure were associated with changes to thyroid hormonal levels. A large human study (29) showed that blood Cd was positively associated with FT3 and urinary Cd was positively associated with FT4.
It may also lower levels of both T4 and T3 (perhaps if iodine and selenium are low) which was shown in animal studies. Obviously as Cd levels accumulate, eventually T3 levels will be decreased due to lowered levels of T4 and selenium resulting in hypothyroidism. A study in children demonstrated that Cd increases TSH levels and decreases thyroid hormone T4 (15).
People who had a thyroidectomy might be more vulnerable to lung damage by exposure to Cd (11). Smoking would not be recommended.
Other thyroid changes and thyroid cancer (22) may also be seen with cadmium toxicity. Cancer may also be more advanced with cadmium toxicity.
“The accumulation of cadmium in thyroid tissue may be one of important etiologic factors for the thyroid cancer progression and aggravation in Korean women.”(21)
“Colloid cystic goiter, adenomatoid follicular hyperplasia with low-grade dysplasia and thyroglobulin hypo- and asecretion, and parafollicular cell diffuse and nodular hyperplasia and hypertrophy are often found in chronic cadmium toxicity.” (20)
Test for Cadmium:
Comprehensive Urine Profile (better for detection of long time Cd exposure), serum Cadmium and mineral hair analysis
How to reduce Cadmium in the body:
The medical system uses chelators such as DMPA for cadmium removal from the body in case of detected toxicity.
However, there are ways to decrease Cd uptake and increase removal in the body and they are:
- Consider stopping smoking, avoid secondary cigarette smoke
- Limit occupational/environmental exposure
- Support glutathione production in the body (glutathione requires selenium and precursors such as glycine, glutamine, cysteine).
- Support glutathione conjugation in liver which detoxifies body from heavy metals. The nutrients required for this step are methionine, amino acids cysteine and taurine, glycine, vitamin C and vitamin B6. Brassica vegetables, such as cabbage, cauliflower, kale, and broccoli and allium vegetables, such as onions, garlic, shallots also help. Vitamin E, N-acetyl cysteine (NAC), bioflavonoids supplementation and fermented vegetables may also be helpful to improve glutathione conjugation. Brewers’ yeast has glutathione building nutrients. One of the best ways is to consume fermented vegetables with liver cleansing herbs. Dandelion root, milk thistle, coriander herb, horseradish and wasabi may also be helpful. Probiotics may also help.
- Avoid environmental exposure in food (organic diet, increasing fibre, detoxifying vegetables, herbs, avoiding refined food). Fibre removes toxins by binding to them.
- Chlorella, sea algae may help but since it is high in iodine, it can aggravate Graves’ disease but may help people with low iodine. Selenium levels needs to be adequate. MetalAway is one of the products a holistic doctor may prescribe in case of metal toxicity.
- Hormone balancing (for example, insufficiency of thyroid hormones compromises liver function and detoxification).
- Adrenal support, stress reduction and better stress management may help.
- Coenzyme Q10 may play a positive role as an agent for treatment of CD poisoning (6)
- Carotenoids were found to increase Cd excretion from the body in study in rats (7), (present in red and orange vegetables, if you use carrots for carotenoids source, use organic carrots and peel them before use)
- Diet which includes selenium and glutathione producing nutrients.
- Vitamin C (28)
- Vitamin D
- Correcting iron deficiency
- Checking zinc and copper levels
- Reducing alcohol consumption as alcohol can increase cadmium uptake
- Alpha-lipoic acid
- Fruit pectin (soluble fibre), psyllium
- Olive leaf supplement
- Willson recommends near infrared sauna for cadmium removal
- Milk consumption may increase Cd uptake (as it is rich in hormones), especially with iron deficiency.
This post is for educational purposes only. Consult your doctor in regards to cadmium and before taking any supplements and dietary changes.
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