The thyroid gland, essential for regulating metabolism and hormonal balance, is particularly sensitive to external influences. In recent years, an increasing body of research has highlighted how exposure to environmental chemicals, pesticides, and industrial pollutants—classified as endocrine disruptors—can interfere with the proper functioning of the neuroendocrine system. These substances can enter the body through various channels, from the air we breathe to the food we eat. Prolonged exposure not only disrupts hormonal balance but may also trigger immune system alterations, contributing to the development of autoimmune thyroid diseases.

How do environmental chemicals like pesticides and pollutants affect thyroid function?

We explore this topic with Professor Paola Grilli, an endocrinologist at Ars Medica.

Exposure to environmental toxins such as pesticides and industrial pollutants can impair thyroid function in a number of ways:

• Endocrine Disruptors: Chemicals like bisphenols (e.g., BPA), phthalates, and polychlorinated biphenyls (PCBs) can mimic or block natural hormones, thereby disrupting normal thyroid activity.

• Perchlorate: Found in some pesticides and fertilizers, perchlorate interferes with iodine uptake, a mineral crucial for thyroid hormone production. High levels of perchlorate can increase TSH (thyroid-stimulating hormone) and decrease circulating thyroid hormone levels.

• Thiocyanates and Nitrates: Commonly found in fertilizers and certain pesticides, these substances compete with iodine, impeding its absorption and disrupting hormone synthesis.

• Isoflavones: Present in soy products and some pesticides, isoflavones can inhibit thyroid peroxidase, an enzyme critical for thyroid hormone production—potentially raising the risk of autoimmune thyroiditis.

• Benzophenone-3: Often used in cosmetics, this compound may alter thyroid hormone levels and impair thyroid function.

• Parabens and Triclosan: These antimicrobial agents, found in many hygiene and food products, may affect thyroid health through endocrine-disrupting mechanisms.

The chronic or repeated exposure to these substances poses a significant threat to thyroid health. Minimizing contact with such chemicals and maintaining a balanced diet rich in iodine and other essential nutrients can help safeguard thyroid function.

s there a link between air pollution and thyroid disorders such as hypothyroidism or hyperthyroidism?

Yes, a growing body of evidence shows a connection between air pollution and thyroid disorders, including both hypothyroidism and hyperthyroidism. Several studies suggest that environmental pollutants can significantly impact thyroid function. Key findings include:

• Particulate Matter (PM2.5 and PM10): Exposure to fine and coarse particulate matter during pregnancy has been associated with a heightened risk of congenital hypothyroidism in newborns. It has also been linked to elevated levels of total thyroxine (TT4) in premature infants.

• Polycyclic Aromatic Hydrocarbons (PAHs): Found in tobacco smoke and combustion-related pollution, PAHs can disrupt thyroid function and increase the risk of related disorders.

• Carbon Monoxide (CO): This pollutant may interfere with the synthesis of thyroid hormones, impairing thyroid performance.

• Sulfur Dioxide (SO₂) and Nitrogen Dioxide (NO₂): Common in urban pollution, these gases can lead to thyroid dysfunction via inflammatory and oxidative stress pathways.

• Ozone (O₃): Ozone exposure has been linked to an increased risk of both hypothyroidism and hyperthyroidism.

• Benzene: This chemical, present in polluted air, can adversely affect thyroid function and raise the risk of thyroid diseases.

Long-term or repeated exposure to these pollutants can have detrimental effects on thyroid health. Strategies to reduce exposure and a nutrient-rich diet are crucial to maintaining thyroid balance.

How do climate change and shifting global dietary habits affect thyroid health?

Climate change and modern dietary trends are emerging as significant factors influencing thyroid function. Here's how:

Climate Change

• Extreme Temperatures: Excessive heat can affect thyroid function, particularly in individuals with preexisting thyroid issues. For example, elevated body temperatures can worsen hyperthyroid symptoms such as excessive sweating and rapid heartbeat.

• Heat Stress: Chronic exposure to extreme heat can cause physical and mental stress, indirectly impairing thyroid function.

Global Dietary Trends

• Iodine Deficiency: Iodine is critical for thyroid hormone synthesis. A decline in iodized salt consumption and changes in food sources can lead to iodine deficiency and related thyroid disorders.

• Western Diet: Diets high in saturated fats and sugars are linked to obesity and metabolic disorders that negatively affect thyroid health.

• Animal vs. Plant Fats: Excessive intake of animal fats may raise the risk of thyroid dysfunction, whereas diets rich in plant-based fats, such as those found in nuts and whole grains, appear to support thyroid health.

Consequences

• Hypo- and Hyperthyroidism: Thyroid disorders often manifest as underproduction (hypothyroidism) or overproduction (hyperthyroidism) of hormones.

• Autoimmune Diseases: Poor dietary habits have been associated with an increased risk of autoimmune thyroid conditions, including Hashimoto's thyroiditis.

How does environmental stress—from climate change to pollution and noise—contribute to hormonal imbalance?

Environmental stressors can significantly influence hormonal health through several mechanisms:

• Cortisol Overproduction: Environmental stress raises cortisol, the primary stress hormone. Chronically high cortisol levels can disrupt the balance of other hormones, including thyroid hormones, estrogen, and testosterone.

• Oxidative Stress and Inflammation: Pollutants can induce oxidative damage and inflammatory responses, harming hormone-producing cells and impairing their function.

• Endocrine Disruption: Many pollutants contain chemicals that act as endocrine disruptors, mimicking or inhibiting natural hormones. Substances like bisphenols and phthalates are known offenders.

• Noise and Psychological Stress: Chronic exposure to loud environments can increase psychological stress, further affecting hormonal regulation.

• Climate-Induced Stress: As global temperatures rise, the body is forced to adapt to new thermal environments, which can place strain on endocrine organs, including the thyroid.

Mitigating these environmental stressors can play a key role in preserving hormonal balance and overall endocrine health.

To what extent can diet and contaminated food impact thyroid function and hormone production?

Diet plays a crucial role in thyroid health, and the presence of contaminants in food can significantly disrupt hormonal regulation:

• Iodine: This micronutrient is essential for thyroid hormone production. Deficiencies—often due to poor dietary intake—can lead to hypothyroidism. Good sources include seafood, seaweed, and Brazil nuts.

• Selenium: Important for thyroid enzyme function, selenium is found in foods like Brazil nuts, sunflower seeds, and fish.

• Goitrogens: Found in foods like soy, cabbage, broccoli, and cauliflower, these compounds can hinder iodine absorption and thyroid hormone production when consumed in excess.

• Heavy Metals: Exposure to lead, mercury, and other heavy metals through food or water can impair thyroid function and contribute to hormonal imbalances.

• Endocrine Disruptors: Chemicals such as BPA and phthalates—found in certain plastics and pesticides—can bind to thyroid hormone receptors or inhibit hormone synthesis.

• Nutrient Deficiencies: Lack of essential vitamins and omega-3 fatty acids can weaken thyroid function.

• Contaminated Foods: Consuming food tainted with pesticides or harmful chemicals increases the risk of thyroid dysfunction.

Adopting a nutrient-rich, well-balanced diet and avoiding exposure to food-based contaminants are key strategies in maintaining thyroid and hormonal health.