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The Spokesman-Review Newspaper
Spokane, Washington  Est. May 19, 1883

People’s Pharmacy: Does fluoride in water affect thyroid function?

 (The Spokesman-Review)
By Joe Graedon, M.S., and Teresa Graedon, Ph.D. King Features Syndicate

Q. I have Hashimoto’s autoimmune hypothyroid disease. I did not feel well taking just Synthroid. When I started taking Unithroid along with a small dose of Cytomel, that worked much better for me.

Most doctors only test the TSH level and then treat that number. Testing free T4 and free T3 is a much better indicator of real thyroid activity.

I have heard that fluoride has a negative effect on the thyroid. Is that true?

A. Fluoride remains a controversial water treatment. On the one hand, dentists promote the use of fluoridated water and toothpaste to prevent tooth decay.

On the other hand, there is some data linking exposure to high levels of fluoride with an increased risk for hypothyroidism. A systematic analysis of 10 studies concluded: “The study has shown a positive correlation between fluoride and hypothyroidism, which is an alarming issue.” (Indian Journal of Dental Research, May-June 2018).

A recent study from Canada found that: “In this Canadian pregnancy and birth cohort, fluoride in drinking water was associated with risk of primary hypothyroidism in pregnant women.” (Science of the Total Environment, April 15, 2023) Scientists believe that fluoride may interfere with the deiodinase enzymes that convert inactive T4 hormone to active T3.

Q. You have written about the pros and cons of cortisone injections. Have the effects on weight been studied?

I had steroid shots in my knees every three months for two years. I recently compared notes with a friend who has a similar history. Both of us gained weight – 35 pounds for me and 40 pounds for her. My blood sugar rose and, sadly, my arthritis got worse.

A. Many people are under the mistaken impression that a corticosteroid injection into a joint has only local effects. In reality, such shots can affect the entire body. Some people report insomnia and anxiety after an injection. Others have trouble controlling their blood sugar. Prolonged corticosteroid treatment is also linked to weight gain (Allergy, Asthma & Clinical Immunology, Aug. 15, 2013).

Q. My doctor recently told me that my vitamin D levels are low. I have not been taking vitamins, because I have to take blood pressure medicines and I hate taking pills. Do I really need to take vitamin D? Is there a gummy or a liquid preparation that would be just as good as a pill?

A. Low vitamin D levels can contribute to a wide range of health problems, from muscle pain and an increased risk of infection to high blood pressure and kidney disease. We would encourage you to skip the gummies because has found that they don’t always provide an accurate dose.

Nonetheless, if you need calcium as well as vitamin D3, L’il Critters and Kirkland (Costco) products both passed the tests. We suggest you spring for the entire report, as the company updates it from time to time. They have recommended a liquid form, Source Naturals Vitamin D-3, as meeting labeling expectations. The complete report is available at subscription-based

You can learn more, including appropriate doses for supplementation, from our “eGuide to Vitamin D and Optimal Health.” This online resource is found under the Health eGuides tab at

In their column, Joe and Teresa Graedon answer letters from readers. Write to them in care of King Features, 628 Virginia Drive, Orlando, Fla., 32803, or email them via their website: Their newest book is “Top Screwups Doctors Make and How to Avoid Them.”