Fluoride Effects on the Thyroid: A Silent Factor Fueling Hypothyroidism

Fluoride effects on the thyroid are becoming a growing topic of concern. Thyroid disorders are more common than ever, and rates of hypothyroidism in particular continue to rise worldwide. The American Thyroid Association estimates that one in eight women will develop a thyroid disorder in her lifetime, which is a staggering number. If you are suffering from fatigue, sluggish metabolism, or hair loss, you are not alone!

Nutrient insufficiencies, poor liver function, genetics, and autoimmune conditions all play impactful roles in fueling thyroid disorders and hypothyroidism. However, many people overlook environmental disruptors that can quietly impact thyroid function. In this blog we’ll focus on a specific environmental factor, fluoride, and how it could be fueling hypothyroidism.

Thyroid Function 101: A Critical Piece of Your Hormonal Symphony

Your thyroid is part of a finely tuned hormonal network known as the HPT (hypothalamic-pituitary-thyroid) axis. This cascade begins in the brain, where the hypothalamus signals the pituitary gland to release TSH (thyroid-stimulating hormone), which then prompts the thyroid gland to produce thyroxine (T4), the inactive form of thyroid hormone.

T4 then has to be converted into triiodothyronine (T3), the active form of thyroid hormone. This primarily occurs in the liver. Together, T4 and T3 regulate metabolism, energy, temperature control, and hormone balance throughout the body. 

These processes of thyroid hormone production and conversion depend on important minerals like selenium, zinc, iron, and iodine. Minerals like selenium and zinc even help buffer detrimental effects of oxidative stress on the body. When we lack adequate levels of these minerals, or when compounds interfere with their digestion and absorption, thyroid activity falters.

Fluoride is one of these compounds. Though technically a mineral, its effects on thyroid cells are the opposite of supportive minerals like iodine, selenium, and zinc.

How Fluoride Interacts with the Thyroid Gland

Fluoride is a mineral that naturally can be found in the soil. However, since the mid-1940s it has also been added into drinking water and dental products to prevent tooth decay given concerns of fluoride deficiency at that time. 

Fluoride is a member of the halogen family, alongside iodine, bromine, and chlorine. Because these elements are similar in structure, fluoride can compete with iodine for uptake into the thyroid gland. Iodine is required for building thyroid hormones, therefore less iodine available to thyroid cells results in a direct reduction in T4 thyroid hormone production.

Another way that fluoride impacts thyroid hormone production is by suppressing thyroid peroxidase (TPO), a key enzyme responsible for converting iodine into thyroid hormones. Having less inactive T4 available will inevitably lead to less active Free T3 thyroid hormone. With less Free T3, the brain will increase TSH levels as it tries to signal to the thyroid to work harder. This is a common pattern seen in early hypothyroidism.

Linking Excess Fluoride and Hypothyroidism

The connection between fluoride and suppressed thyroid activity is not new. In fact, high doses of fluoride were once used therapeutically to treat thyroid overactivity (hyperthyroidism) because of fluoride’s known ability to slow thyroid hormone production.

Research supports this connection worldwide. A case-controlled study in Iran showed that people exposed to higher levels of fluoride in drinking water had significantly lower T3 and T4 levels and higher levels of TSH. Another study conducted in England revealed that communities with fluoridated water had nearly double the prevalence of hypothyroidism compared to those living in areas with non-fluoridated water. 

A recent meta-analysis that looked at over 25 studies found a clear association between fluoride in drinking water above 2 mg/L and TSH levels. In the United States, water is often fluoridated to levels between 0.7-1.2 mg/L, although actual levels vary by community. Of course, observational studies cannot prove direct causation, but the correlation between higher levels of fluoride being linked to hypothyroidism cannot be ignored.

Fluoride has also been shown to impact thyroid activity more severely in cases of low or deficient iodine levels. We know just how important iodine is for thyroid gland function and thyroid hormone production. Insufficient iodine levels can even lead to thyroid nodules or an enlarged thyroid. Low iodine levels, which are very common given widespread mineral-deficient diets, on top of excess fluoride, serve as a double burden on the thyroid. 

A Functional Approach to Supporting Optimal Thyroid Function

If you’re struggling with low thyroid symptoms such as fatigue, cold intolerance, brain fog, and hair thinning, it’s critical to give your body the thyroid-supportive nutrients it needs, and remove factors standing in the way. 

Through intentional nutrition support, namely mineral-rich foods and targeted supplementation, you can effectively boost iodine, selenium, zinc, and magnesium intake for a more resilient thyroid. 

Further optimize thyroid function by reducing your exposure to compounds like fluoride that can impair thyroid activity. Fluoride is often found in water and dental products, which we encounter all day, every day! Reverse osmosis water filters (like the AquaTru Systems) effectively remove fluoride from drinking water. 

For fluoride-free dental care, we love Risewell Hydroxyapatite Toothpaste (use code functionalfueling10 for a discount), which protects your enamel without the endocrine-disrupting effects. Listen into our conversation with the co-founder of Risewell on this episode of the Strength in Hormones podcast.

Because women are more susceptible to developing thyroid issues, it’s essential to accurately assess your thyroid function. This is particularly important for those predisposed to autoimmune conditions or with a family history of thyroid disease. Comprehensive thyroid testing goes beyond TSH alone to look at a more complete picture of thyroid activity. For a full rundown, check out this blog here.

Want a Complete Guide to Optimizing Your Thyroid Function?

While fluoride was introduced into our environment for its role in strengthening tooth enamel, we now know that it doesn’t come without other impacts on the body, particularly thyroid function. Chronic fluoride exposure can fuel hypothyroidism, especially when key thyroid nutrients like iodine may be low.

Support optimal thyroid function by reducing fluoride exposure, accurately assessing your thyroid function with comprehensive testing, and setting a foundation of thyroid-supportive nutrition and lifestyle practices. This is exactly what you’ll find in our Functional Thyroid Foundations group program! Our 4-week program provides a clear roadmap of the nutrition and lifestyle practices and strategies to help optimize your thyroid function and therefore overall hormone health. 

This is not just for our friends with hypothyroidism! This program was created to help decrease inflammation, improve blood sugar balance, and support energy levels to help prevent thyroid issues and optimize thyroid function for more vibrant health.  Join the waitlist today as we countdown our next live program beginning soon! We can’t wait to see you there!

Written by Romana Brennan, MS, RDN