Environmental Causes of Thyroid Disease

Thyroid Overview

The thyroid gland functions as the body's metabolic regulator, orchestrating a complex interplay of hormones to maintain balance. Its primary task is to produce and release two key hormones, thyroxine (T4) and triiodothyronine (T3), into the bloodstream. This process is tightly regulated by the hypothalamus and pituitary gland through a feedback loop. When thyroid hormone levels drop, the hypothalamus releases thyrotropin-releasing hormone (TRH), which signals the pituitary gland to produce thyroid-stimulating hormone (TSH). TSH then prompts the thyroid gland to release T4 and a smaller amount of T3. Once in circulation, T4 can be converted into the more metabolically active T3 in various tissues throughout the body. T3 and T4 regulate the menstrual cycle, metabolism, energy levels, mood, body temperature, blood pressure, heart rate, and many other critical physiological processes. Through this intricate system of hormonal control, the thyroid gland ensures the body's metabolic functions remain balanced and optimized for health and vitality. This delicate balance can be disrupted by certain chemicals known as endocrine disruptors. These chemicals, prevalent in our environment, can interfere with the endocrine system's normal function and significantly impact thyroid health.

What are Endocrine Disruptors?

Endocrine disruptors are harmful substances that interfere with the synthesis, secretion, transport, metabolism, binding action, or elimination of hormones. Endocrine disruptors can increase the production of certain hormones, decrease the production of others, imitate hormones, turn one hormone into another, bind to essential hormones stopping them from working, cause premature cell death, compete with essential nutrients, and accumulate in organs that produce hormones. Exposure to endocrine disruptors has been strongly linked to thyroid disease, including hypothyroidism, hyperthyroidism, and thyroid cancer. Substances such as polychlorinated biphenyls (PCBs), bisphenol A (BPA), perchlorate, phthalates, and flame retardants can adversely affect thyroid health. They can also contribute to autoimmune thyroid disorders by triggering an immune response against the thyroid gland. Several endocrine-disrupting chemicals have been linked to thyroid disease, including:

Phthalates

Phthalates, a class of chemicals widely used as plasticizers in plastics and frequently found in personal care items, have garnered attention for their potential impact on thyroid health. Research indicates that phthalates not only disrupt thyroid hormone levels but also impede iodine uptake, an essential mineral for thyroid hormone synthesis. Despite their rapid metabolism and excretion primarily through urine, some phthalate residues persist in the body over the long term. These lingering compounds continue to exert adverse effects, notably interfering with the production of thyroxine (T4) and influencing the function of thyroid hormone receptors. Exposure to phthalates can come from various sources such as food packaging, fast food wrappers, children's toys, scented products containing undisclosed "fragrance," and even inhalation of contaminated air. Phthalates do not chemically bind to materials, allowing them to readily release from added products. Limiting the consumption of foods stored in plastic packaging and avoiding microwaving plastic containers can help reduce exposure through food sources. Similarly, avoiding products labeled with the #3 recycling symbol or containing PVC can mitigate exposure to phthalates. Opting for PVC and phthalate-free alternatives and limiting hand-to-mouth contact with phthalate-containing products further reduces exposure risks. Assessing body care products for phthalates and choosing phthalate-free options can also help minimize exposure through personal care routines. Additionally, considering the use of air purifiers and water filters can further reduce exposure to phthalates present in indoor air and water sources.

Bisphenol A (BPA)

Similar to phthalates, Bisphenol A (BPA) is predominantly found in plastic products. BPA tends to migrate into food and beverages, especially when containers are heated, making it a prevalent route for exposure. While ingestion accounts for the majority of BPA exposure, it can also permeate the skin. Following absorption, BPA can accumulate in bodily tissues or be eliminated through perspiration or urinary excretion. Its presence extends to various everyday items, including receipt paper, food packaging, plastic water bottles, canned food linings, sports gear, and dental materials like sealants and composites. Even with the abundance of products labeled "BPA-free," it's essential to stay cautious, as alternatives such as BPS and BPF could still pose comparable risks to thyroid health. Similar recommendations for minimizing BPA exposure mirror those suggested for phthalates.

Polychlorinated Biphenyls (PCBs)

Despite being banned in 1977 due to their health risks, Polychlorinated Biphenyls (PCBs) continue to persist in the environment today owing to their slow degradation rate. PCBs continue to exert detrimental effects on thyroid function, due to their ability to reduce T3 and T4 hormone levels and raise anti-thyroid antibodies. These harmful chemicals enter the body through multiple pathways, including ingestion, inhalation, and skin contact. Upon entry, PCBs circulate in the bloodstream, accumulating in vital organs such as the brain, liver, and even breast milk, where they persist for years post-exposure. Common sources of ingestion include contaminated seafood, dairy, eggs, and fatty meats, while environmental exposure stems from living in proximity to incinerators, hydraulic fluids, lubricating oils, and a plethora of industrial materials such as plasticizers, sealants, and thermal insulation. Avoiding consumption of contaminated seafood, particularly fish known to accumulate PCBs, can significantly reduce exposure. Choosing organic foods, especially dairy and meat products, can help lower PCB intake, as PCBs tend to accumulate in the fat of animals. Implementing measures to reduce exposure to indoor sources of PCBs, such as contaminated building materials, electrical equipment, and old fluorescent light fixtures, can further mitigate risk.

Polybrominated Diphenyl Esters (PBDEs)

Polybrominated Diphenyl Ethers (PBDEs) are used as flame retardants in a variety of consumer products, including electronics, furniture, mattresses, car seats, strollers, textiles, and plastics. PBDEs are known to imitate thyroid hormones and disrupt their activity. PBDEs are very persistent and hard to avoid. The best ways to cut down on exposure are to use a vacuum cleaner with a HEPA filter, steer clear of foam mattress pads, avoid reupholstering foam furniture, take caution when replacing old carpet, and buy PBDE-free clothing and furniture.

Perchlorate

Perchlorate, a chemical utilized in fertilizers, fireworks, road flares, explosives, and rocket fuel, also holds approval for food contact applications, enabling its migration into food and water sources. Perchlorate disrupts thyroid iodine uptake, thereby impeding thyroid function and hormone synthesis. To safeguard against perchlorate exposure, opting for reverse osmosis filtered water and ensuring adequate dietary iodine intake are prudent measures. However, it's crucial to exercise caution with iodine supplementation and consult a healthcare professional beforehand, as improper usage may exacerbate thyroid issues.

Pesticides

The correlation between thyroid disorders and regions with elevated pesticide usage is strikingly evident. Pesticides encompass a broad category of chemicals aimed at warding off weeds, diseases, or pests. Pesticides persist in soil, where they accumulate over time, and can be taken up by plants as they grow, leading to potential human exposure through consumption. Animals grazing in pesticide-treated areas may also accumulate these substances in their fat stores. Opting for organic produce whenever possible and proactively engaging local farmers regarding their pesticide practices can offer a proactive approach to mitigating potential exposure and safeguarding thyroid health.

Heavy Metals

While the exact mechanisms underlying heavy metal-induced thyroid dysfunction remain unclear, it is evident that metals such as mercury, lead, and cadmium can inflict damage on the thyroid and elevate the likelihood of autoimmune thyroid conditions. Although complete avoidance of heavy metals may be impractical, proactive measures can reduce exposure. Mercury, prevalent in select fish and silver dental fillings, poses a notable risk. Lead and cadmium, found in contaminated water and soil, are additional concerns, with cadmium particularly concentrated in cigarette smoke. By adopting strategies to minimize exposure to these heavy metals, individuals can help alleviate the burden on their thyroid health.

Endocrine disruptors are pervasive in our environment and pose a significant risk to thyroid health. By understanding their sources and mechanisms of action, we can take proactive steps to reduce exposure and protect our thyroid function. Staying informed and advocating for safer products and regulations are crucial in combating the impact of these harmful chemicals. Prioritizing your thyroid health through lifestyle choices and awareness is an essential step toward overall well-being.