Fluoride and Hypothyroidism

Fluoride and Hypothyroidism

Fluoride and Hypothyroidism
© Jcomp on Freepik

Hypothyroidism is a condition where the thyroid gland doesn’t produce enough thyroid hormones. These hormones, thyroxine (T4) and triiodothyronine (T3), are crucial for regulating metabolism, growth, and development. People with hypothyroidism, especially if untreated, may experience symptoms such as fatigue, weight gain, cold intolerance, dry skin, depression, and slowed heart rate.

Fluoride is a mineral found naturally in some water sources and added to many public water supplies to promote strong teeth and prevent dental caries (cavities). It is also added to toothpaste, mouth rinses, and occasionally to table salt. While its dental benefits are well documented, concerns about potential adverse health effects have been raised over the years. One area of concern is the possible link between fluoride and hypothyroidism.

In this article, we will look at some key research findings to understand this connection. We will also address the general public health perspective on water fluoridation.

What is the Connection between Fluoride and Thyroid Function?

To understand this connection, we first need to draw a link between fluoride and iodine. The thyroid gland uses iodine from diet to produce thyroid hormones. Fluoride, which is chemically similar to iodine, can interact with the thyroid in several ways. The main concern, however, is that fluoride may inhibit the thyroid’s ability to absorb iodine because fluoride can easily displace iodine in the body. Also, some studies suggest that fluoride can interfere with the deiodinase enzymes that convert T4 into the more active T3 hormone.

Research Findings

According to a comprehensive review of EPA’s standards by the U. S. National Research Council (NRC) in 2006, research dating back to the late 1900s indicated that in areas with high fluoride concentrations in water (above 4 mg/L), there were higher instances of goiter (a visibly enlarged thyroid gland). These findings initially triggered concerns about fluoride’s impact on thyroid health. The NRC report also references several studies, including animal studies, that observed an association between high doses of fluoride and thyroid dysfunction. However, translating these findings to humans is complex due to differences in metabolism and exposure levels.

Interestingly, some population-based studies have also found a correlation between high levels of fluoride exposure and increased rates of hypothyroidism. One notable example is a study published in the Journal of Epidemiology & Community Health in 2015 that examined the rates of hypothyroidism in areas of England with fluoridated water versus non-fluoridated water. This study found that high levels of fluoride in water were associated with a 30% higher prevalence of hypothyroidism. However, the study faced criticism for its approach, which only highlighted correlation and could not conclusively prove causation. Another argument raised against this study, in line with other critical commentaries on this study, is that it did not adequately control for other factors that could influence thyroid health.

What are the Public Health Perspectives on Water Fluoridation?

The addition of fluoride to public water supplies is endorsed by numerous health organizations worldwide — including the World Health Organization (WHO), the Centers for Disease Control and Prevention (CDC), the American Dental Association (ADA), and the British National Health Service (NHS UK) — as a safe and effective measure to reduce dental decay. These organizations continue to support water fluoridation, emphasizing that the levels used in public water supplies are safe for the general population. In fact, the CDC considers water fluoridation one of the ten great public health achievements of the 20th century due to its role in significantly reducing the prevalence of dental decay in the United States.

The current level of fluoride recommended for public water fluoridation, as recommended by the U.S. Department of Health and Human Services is 0.7 mg/L. The U.S. Environmental Protection Agency (EPA) has also set a maximum contaminant level for fluoride in drinking water at 4 mg/L, which is designed to prevent skeletal fluorosis, another potential side effect of excessive fluoride intake.

On a global level, however, public health policies on water fluoridation are varied and influenced by a couple of factors like local environmental conditions, dietary factors affecting iodine levels, and public opinion. In North America, fluoride is commonly added to water supplies and is supported by major health organizations, assuming adequate iodine intake. Europe shows mixed approaches with some countries like the UK having specific fluoridated areas, while many others do not fluoridate their water at all. In parts of Asia and Africa, the challenge is often dealing with naturally high levels of fluoride which can exceed safe limits, leading to concerns about both fluorosis and thyroid health. Australia supports water fluoridation broadly and follows guidelines similar to North America regarding its safety concerning thyroid health.

Key takeaways

  • Research suggests that iodine deficiency might make people more susceptible to the potential effects of fluoride on the thyroid.
  • While there is some evidence suggesting that excessive fluoride exposure could contribute to hypothyroidism, especially in populations with iodine deficiency, the risk at levels typically found in public water systems and dental supplies is considered low. 
  • Although the public health policies on water fluoridation vary globally, many countries strive to ensure that the amount of fluoride in public water supplies is carefully monitored and well below levels that might cause problems. 
  • If you have concerns about your thyroid health or suspect you might have hypothyroidism, talk to your doctor. They can run tests to check your thyroid function and determine the cause if there’s really an issue.
  • If you’re particularly worried about your fluoride intake, you can also discuss this with your doctor. They can advise you based on your specific situation.
  • More research is needed to address unresolved questions and ensure public health policies reflect the most current scientific understanding. 
  • This ensures the dual goals of protecting dental health while minimizing any potential risks to overall health, including thyroid function.


At ThyForLife, we do our utmost to provide accurate information. For detailed medical information regarding diagnosis, treatment, and general practices please consult your healthcare professional. Always listen to the advice of your healthcare provider.
Share this article

You might also like

Showing most popular and related articles for you

Be the first to get

weekly thyroid related articles and useful tips directly to your inbox!