Recently, I have found information that fluoride affects normal endocrine function and therefore affects activity of the thyroid gland (source). I searched for other publications on this topic and I was surprised to find that the relation between fluoride and thyroid disorders is no news anymore.
U.S. National Research Council of the National Academies (NRC) announced in 2006 (8 years ago) that fluoride has a broad range of effects on endocrine system (source). Fluoride stimulates or inhibits the secretion of hormones. It does it directly or indirectly e.g. through distorting calcium balance or hinder enzymes that are needed for activation of the normal hormones.
The influence of fluoride is so strong that (based on evidence indicating that smallest amounts of 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 (thyroid with too high activity) (Merck Index 1968). Remarkably, fluoride therapy (2-5 mg /day over several months (Galletti & Joyet 1958)) reduced thyroid activity in the treated patients (McClaren 1969; Galletti 1958; May 1937).
The question remains if fluoride contributes to hypothyroidism (thyroid with too low activity). A concern arises upon evidence that:
- fluoride can exacerbate the anti-thyroid effects of iodine deficiency (Gas’kov 2005; Hong 2001; Wang 2001; Zhao 1998; Xu 1994; Lin 1991; Ren 1989; Guan 1988)
- fluoride can cause goiter in some individuals
- fluoride can alter thyroid hormone levels in a manner consistent with a general thyroid suppressant
Fluoride and Iodine Deficiency
Iodine is the basic building block of the T3 and T4 hormones and thus an adequate iodine intake is essential for the proper functioning of the thyroid gland. When iodine intake is inadequate during infancy and early childhood, the child’s brain can suffer permanent damage, including mental retardation. (Iodine deficiency is the leading cause of mental retardation throughout the world.). In China, researchers have repeatedly found that an iodine deficiency coupled with fluoride exposure produces a significantly more damaging effect on neurological development than iodine deficiency alone (Hong 2001; Xu 1994; Lin 1991; Ren 1989).
Fluoride and Hypothyroidism/Hashimoto’s
- In clinical hypothyroidism, the thyroid gland fails to produce sufficient quantities of the hormones triiodothyronine (T3) and thyroxine (T4). These hormones are required by all metabolically active cells, and their reduced presence can thus produce a range of ill effects, including fatigue, muscle/joint pain, depression, weight gain, menstrual disturbances, impaired fertility, impaired memory, and inability to concentrate. When T3 and T4 levels begin to fall, the pituitary gland responds by increasing production of “Thyroid Stimulating Hormone” (TSH) as a means of getting the thyroid to produce more T3 and T4.
- In subclinical hypothyroidism, the TSH level is elevated, but the T3 and T4 hormones are still within the normal range. Although subclinical hypothyroidism used to be regarded as largely inconsequential, it is increasingly considered a “clinically important disorder” (Gencer 2012). Some studies have found, for example, that subclinical hypothyroidism in pregnant women results in reduced IQ in offspring, (Klein 2001; Haddow 1999), and a recent study in the Journal of the American Medical Association found that adults with subclinical hypothyroidism had a significantly higher rate of coronary heart disease (Rodondi 2010).
Studies investigating fluoride’s impact on thyroid hormone levels have produced divergent findings, but are consistent with fluoride having an anti-thyroid effect under certain circumstances (NRC 2006). The most common thyroid effect associated with fluoride exposure appears to be an increase in TSH levels, with or without a corresponding effect on T3 or T4 (Susheela 2005). One of the most recent studies, for example, found a trend towards higher TSH in children based on the severity of their dental fluorosis, but without a significant effect on either T3 or T4 (Hosur 2012). These and other findings indicate that fluoride can contribute to a subclinical, if not clinical, hypothyroid condition. It remains difficult to predict the toxic dose, however, as it appears to depend, in part, on the nutritional and health status of the individual, particularly the adequacy of iodine intake (NRC 2006).
Common Sources of Fluoride Include
- Bottled beverages – due to fluoride content in water
- Black tea
- Red tea
- Canned food items
- Black/red rock salt
- Chewing tobacco
It is definitely something I am going to consider. I am glad that I use fluoride free tooth paste for two years now. When it comes to tea, I choose green tea variations. I haven’t been a big fan of canned food for a long time, I try to buy jar foods whenever I have a choice between a can and a jar. Ready beverages aren’t my thing, nothing will beat homemade lemonade :-)
Do you have other information with regard to effect of fluoride? Share with us in comments, please. We all are eager to learn. Our goal is the same, to feel good :-)