Endocrine Disruptors and Thyroid Health: Part 2
Published October 28 2013
In last week’s article I discussed in detail the negative impact of pesticides on the endocrine system. But there are other endocrine disruptors, and in this article I want to discuss some of the other more common ones we’re exposed to. I’ll specifically talk about four xenoestrogens which most people are exposed to on a regular basis. And while you won’t be able to completely avoid them, hopefully reading this information will help you to do things to minimize your exposure to these chemicals.
Before I talk about xenoestrogens and how they affect the endocrine system, along with other areas of the body (i.e. immune system), I want to point out something important. Endocrine disrupting chemicals (EDCs) affect people of all ages. As I explained last week, EDCs can act on the estrogen, androgen, and thyroid hormone receptors (1), and can then bind to and activate different hormone receptors, and by doing this can mimic the natural hormone’s action.
This obviously can have a harmful effect on both adults and children. However, there is no question that children are affected to a greater extent, as such chemicals can affect their growth and development. So while it’s wise for everyone to do everything they can to minimize their exposure to xenoestrogens, it is even more important for children to avoid exposure as much as possible. And unfortunately there are many different areas where xenoestrogens are found, including the following:
Many household products
Nail polish and nail polish remover
Non-organic meat and dairy
Why Are Xenoestrogens Harmful?
The reason why xenoestrogens cause harm is because they are capable of altering the physiology of the body. They can accomplish this in a few different ways. One way is by altering serum lipid concentrations, or metabolism enzymes that are necessary for converting cholesterol to steroid hormones, which in turn will alter the production of the steroid hormones (2). In addition, EDCs can potentially affect different receptors in the body, including the aryl hydrocarbon receptor (AhR), the peroxisome proliferator-activated receptor (PPAR) and retinoid X receptor (RXR), signal transduction pathways, calcium influx, and/or neurotransmitter receptors (2).
In addition to having harmful effects on the endocrine system, xenoestrogens can also cause harm to the immune system (3). There is even some evidence that such chemicals can be involved in the pathogenesis of an autoimmune condition (4) (5). Remember that most people with Graves’ Disease and Hashimoto’s Thyroiditis have a genetic predisposition for these conditions, but most of the time they are triggered by environmental factors. And while it might be far-fetched to consider that someone can develop these conditions due to drinking a lot of water from plastic bottles or using products which have xenoestrogens, one can’t completely dismiss the possibility.
I want to focus on four xenoestrogens which can affect our health. These include Bisphenol A (BPA), phthalates, polychlorinated biphenyls (PCBs), and Polybrominated diphenyl ethers (PBDEs).
Bisphenol A (BPA). Bisphenol A (BPA) is a building block of polycarbonate plastics often used for food and beverage storage, and BPA is also a component of epoxy resins that are used to line food and beverage containers (6). Studies have shown that BPA can leach from these and other products in contact with food and drink, and as a result, routine ingestion of BPA is presumed (6). While studies employing standardized toxicity tests have thus far supported the safety of current low levels of human exposure to BPA, both the National Toxicology Program at the National Institutes of Health and FDA have some concern about the potential effects of BPA on the brain, behavior, and prostate gland in fetuses, infants, and young children (7).
There have been numerous studies which show evidence that BPA can disrupt the endocrine system (8) (9) (10) (11). The question is “how much exposure to BPA (or any endocrine disruptor for that matter) is necessary to disrupt the endocrine system? This is where it gets controversial. As I mentioned earlier, there is no question that it will have a greater impact on the health of infants and children, which shouldn’t come as a surprise. But how many bottles of water does an adult have to drink before BPA causes problem? And as I listed above, bottled water is just one source of this chemical. The truth is, everyone is different, and so despite what studies show, different people will have various reactions to endocrine disruptors such as BPA. Some people might experience problems with the hormones when exposed to low concentrations, while others might not experience problems unless if they are exposed to very large amounts.
As for whether BPA has a direct effect on thyroid health, this is controversial as well. However, a few recent studies do show evidence that this chemical does affect the thyroid gland. One of these studies suggest that BPA exerts a direct effect on the thyroid follicular cell, and that these cells can sense very low amounts of BPA (12). Another study explored the relationship between urinary BPA and thyroid function in a Chinese population, and their results supported previous reports of associations between BPA exposure and altered thyroid hormones (13).
Phthalates. Phthalates are a group of chemicals used to make plastics more flexible and harder to break (14). They are often called plasticizers. They are used in hundreds of products, such as vinyl flooring, adhesives, detergents, lubricating oils, automotive plastics, plastic clothes (i.e. raincoats), and personal-care products (soaps, shampoos, hair sprays, and nail polishes) (14). The Environmental Protection Agency (EPA) is concerned about phthalates because of their toxicity and the evidence of pervasive human and environmental exposure to these chemicals (15).
Just as is the case with BPA, there is strong evidence that phthalates disrupt the endocrine system (16). With regards to thyroid health, one study explored the cross-sectional relationship between urinary concentrations of a couple of different types of phthalates, along with BPA, with a panel of serum thyroid measures in adults and adolescents (17). Among adults they observed significant inverse relationships between phthalates and total thyroxine, free T4, total triiodothyronine (T3), and thyroglobulin, and positive relationships with TSH. In adolescents there was a significant positive relationship between phthalates and total T3. Another study looked to see if phthalates can alter thyroid hormone levels in men (18), and concluded that phthalates may be associated with altered free T4 and/or total T3 levels in adult men, although it did say that additional research is needed to confirm the findings. Yet another study showed negative associations between urinary phthalate concentrations and thyroid hormones in healthy children (19). So whether phthalates have a direct effect on thyroid health is still controversial.
There is also evidence that exposure to phthalates can have a negative impact on the immune system. High levels of phthalates from PVC products can modulate the immune response, and might contribute to the development of asthma in adults (20). Epidemiologic studies in children show associations between indicators of phthalate exposure in the home and risk of asthma and allergies (20). There also seems to be an association between phthalates in indoor dust and allergic symptoms (21). With regards to autoimmunity, the only study I came across involving phthalates was that it can potentially cause lupus in mice (22). So it is unclear whether exposure to phthalates can trigger an autoimmune response in humans, thus leading to Graves’ Disease or Hashimoto’s Thyroiditis.
Polychlorinated biphenyls (PCBs).PCBs belong to a broad family of man-made organic chemicals known as chlorinated hydrocarbons (23). PCBs were domestically manufactured from 1929 until their production was banned in 1979. They have a range of toxicity and vary in consistency from thin, light-colored liquids to yellow or black waxy solids (23). Although no longer commercially produced in the United States, PCBs may be present in products and materials produced before the 1979 PCB ban. Once in the environment, PCBs do not readily break down and therefore may remain for long periods of time cycling between air, water, and soil (23).
Although many people are concerned about eating fish due to heavy metals, PCBs are another toxin to be concerned about. Even smaller fish such as sardines can have high amounts of PCBs. PCBs can also be present in the livestock (24), (25). So while eating organic meat and dairy might limit your exposure to synthetic hormones fed to the livestock, PCBs still might be a problem. This is also another toxin that can be present in tap water, even though certain treatment methods have been used to remove PCBs, resulting in extremely low levels in the drinking water.
As for the effects of PCBs on the endocrine system, one study showed that serum PCB levels and consumption of Great Lakes fish are associated with significantly lower levels of T4 and free thyroxine Index (FTI) in women and with significantly lower levels of T4 in men (26). PCBs may also decrease steroid binding to sex hormone-binding globulin (26). A more recent study showed evidence for a potential toxicological relevance of PCBs in the disruption of thyroid hormone homeostasis (27). Another study demonstrated a reduction in thyroid function in adolescents in relation to their serum levels of PCBs (28). However, another study that looked at the effect of PCBs on thyroid hormone levels in construction workers showed that there was no evidence of thyroid function or immune system involvement (29), although it did involve a small number of participants and low PCB levels.
Polybrominated diphenyl ethers (PBDEs). Polybrominated diphenyl ethers (PBDEs) are a class of flame retardants used in textiles, furniture, and electronic products (30). The EPA is concerned that certain PBDEs are persistent, bioaccumulative, and toxic to both humans and the environment (31). And just as is the case with the other xenoestrogens, there is evidence that PBDEs have a negative impact on the endocrine system.
With regards to thyroid health, there is evidence that PBDEs can bind to the thyroid hormone receptors, thus resulting in a disruption of thyroid hormone function (32). A few different studies have looked at the associations between PBDEs and thyroid health during pregnancy. One study showed that PBDE’s affect thyroid hormone levels in developing fetuses and newborn babies (33). Another study showed that PDBE exposures are elevated in pregnant women in California and suggest a relationship with thyroid function (34). In another study, the authors found no conclusive evidence that prenatal exposure to PBDEs at levels similar to those of the general US population is related to neonatal TSH (35).
Minimizing Exposure To Xenoestrogens Is A Major Challenge
There is no question that reducing one’s exposure to these chemicals are a great challenge. While there are many different actions one can take, I would focus on the following four:
1) Purchase natural household products and cosmetics. I realize this can become expensive, but you shouldn’t overlook the impact that the chemicals included in these products can have on your health. And if you have children this should motivate you even more to use natural and organic products.
2) Try not to drink out of plastic bottles on a regular basis. Once again, this is even more important if you have children. But most adults should also play it safe and minimize drinking water from plastic bottles.
3) Eat organic food. While this probably won’t completely eliminate your exposure to xenoestrogens, eating organic food will greatly minimize your exposure to these toxins.
4) Do things to help eliminate toxins from your body. I’ve discussed this in other articles and posts, and so I won’t discuss this in detail here. But I do think that most people can benefit from doing a liver detoxification once or twice per year, and other methods of detoxification such as sauna therapy and colon hydrotherapy can also help to eliminate these toxins from the body. For more information I would read the blog post I wrote entitled “3 Ways People With Thyroid and Autoimmune Thyroid Conditions Can Detoxify Their Body“.
There are other actions you can take, but I would at least start by focusing on these three areas. With regards to eating organic food, I realize that some people might not be able to purchase organic food, either due to the higher costs, or perhaps they live in a small town or a different country where they don’t have access to organic food. When this is the case all you can do is to try to eat as healthy as you can and focus on the other areas in order to reduce your exposure to these toxins.
In summary, xenoestrogens can have a detrimental effect on the endocrine system. If you read some of the studies you’ll realize that there still is a lot of work to be done in this area. Controversies still exist when it comes to the effect that these chemicals have on our health, and although some of the information may be conflicting, I think there is more than enough evidence out there which shows that exposure to xenoestrogens can cause problems with the endocrine system.