Fluoride was definitively identified as an endocrine disruptor in a 2006 report by the U.S. National Research Council of the National Academies (NRC). This report states:

In summary, evidence of several types indicates that fluoride affects normal endocrine function or response; the effects of the fluoride-induced changes vary in degree and kind in different individuals. Fluoride is therefore an endocrine disruptor in the broad sense of altering normal endocrine function or response, although probably not in the sense of mimicking a normal hormone. The mechanisms of action remain to be worked out and appear to include both direct and indirect mechanisms, for example, direct stimulation or inhibition of hormone secretion by interference with second messenger function, indirect stimulation or inhibition of hormone secretion by effects on things such as calcium balance, and inhibition of peripheral enzymes that are necessary for activation of the normal hormone. (page 266)

The endocrine system is a collection of glands in the body that secrete hormones–chemical signals that regulate the function of numerous cells and organs in the body.  As discussed in the NRC report, the following four glands can each be affected by fluoride exposure:

Thyroid Gland:

The thyroid gland produces the hormones triiodothyronine (T3) and thyroxine (T4), which are required by all metabolically active cells in the body. When the thyroid produces too much, or too little, of these hormones, a myriad number of health consequences arise.

Based on evidence indicating that fluoride can suppress thyroid activity, doctors in Europe and South America once prescribed fluoride as a drug to reduce thyroid gland function in patients with hyperthyroidism (over-active thyroid). Clinical research showed that fluoride ingestion, at relatively low doses, was effective at reducing thyroid function in the hyperthyroid patients. Concerns have thus arisen about the potential for fluoride to contribute to hypothyroidism (under-active thyroid). This concern has been further fueled by evidence showing that (1) fluoride can exacerbate the anti-thyroid effects of iodine deficiency, (2) can cause goiter in some individuals, and (3) can alter thyroid hormone levels in a manner consistent with a general thyroid suppressant. Read more. 

Pancreas:

The pancreas is the gland that produces insulin, a hormone that regulates the uptake of glucose from the bloodstream. Animal and human studies have repeatedly found that fluoride exposure can increase the levels of glucose in the blood. Chronic elevation of blood glucose levels is the hallmark of Type II Diabetes. While the mechanism underlying fluoride’s effect on glucose levels has yet to be determined, some research suggests it could be the result of fluoride’s impact on the quantity of, or cellular responsiveness to, the insulin produced. Read more.

Pineal Gland:

The pineal gland is located between the two hemispheres of the brain and produces the hormone melatonin. Melatonin regulates the body’s circadian rhythm (sleep-wake cycle) as well as the onset of puberty. In the 1990s, a British researcher discovered that fluoride accumulates to very high levels in the calcified part of the pineal gland. The fluoride levels recorded in the pineal gland are, in fact, the highest fluoride concentrations found anywhere in the body. Although the effects of these high concentrations remain poorly understood, animal experiments have found that animals receiving high doses of fluoride had a reduced melatonin production and an earlier onset of puberty. Read more.

Parathyroid Gland

The parathyroid gland produces parathyroid hormone (PTH). PTH regulates the amount of calcium in our bones and blood supply. When the calcium level in blood starts to fall, PTH triggers the breakdown of bone tissue as a means of transferring the body’s stored supply of calcium into the blood supply. When the parathyroid produces too much PTH a condition known as hyperparathyroidism  develops. Hyperparathyroidism has been found to occur as a secondary effect of the fluoride-induced bone disease skeletal fluorosis, and may help to explain some of the bone effects encountered in fluorosis. Read more.

More recently,

in 2012 Vandenberg et al. included sodium fluoride in a list of endocrine disrupting chemicals (EDCs) with low-dose effects. They noted the EDC action of sodium fluoride as: “Inhibits insulin secretion, PTH, TH.” The Vanderberg et al. paper was cited in a larger report, Science of Endocrine Disrupting Chemicals – 2012, co-published in January 2013 by the United Nations Environment Programme and the World Health Organization – see page 13.

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