Uploaded August 2012 | Updated September 2026, 17 minutes ago
When people think of fluoride being prescribed for medicinal purposes, they generally think of fluoride supplementation to reduce tooth decay. Fluoride, however, has also been prescribed as a drug to reduce the activity of the thyroid gland. Up through the 1950s, doctors in Europe and South America prescribed fluoride to reduce thyroid function in patients with over-active thyroids (hyperthyroidism). (Merck Index 1968). Doctors selected fluoride as a thyroid suppressant based on findings linking fluoride to goitre, and, as predicted, fluoride therapy did reduce thyroid activity in the treated patients. (McClaren 1969; Galletti 1958; May 1937). Moreover, according to clinical research, the fluoride dose capable of reducing thyroid function was notably low -- just 2 to 5 mg per day over several months. (Galletti & Joyet 1958). This dose is well within the range (1.6 to 6.6 mg/day) of what individuals living in fluoridated communities are now estimated to receive on a regular basis. (DHHS 1991).
When people think of fluoride being prescribed for medicinal purposes, they generally think of fluoride supplementation to reduce tooth decay. Fluoride, however, has also been prescribed as a drug to reduce the activity of the thyroid gland. Up through the 1950s, doctors in Europe and South America prescribed fluoride to reduce thyroid function in patients with over-active thyroids (hyperthyroidism). (Merck Index 1968). Doctors selected fluoride as a thyroid suppressant based on findings linking fluoride to goitre, and, as predicted, fluoride therapy did reduce thyroid activity in the treated patients. (McClaren 1969; Galletti 1958; May 1937). Moreover, according to clinical research, the fluoride dose capable of reducing thyroid function was notably low -- just 2 to 5 mg per day over several months. (Galletti & Joyet 1958). This dose is well within the range (1.6 to 6.6 mg/day) of what individuals living in fluoridated communities are now estimated to receive on a regular basis. (DHHS 1991).







![Debunked: Study Finding Huge Increase In IQ From Fluoride Exposure Is Biologically Impossible
During the Fluoride Lawsuit, EPA tried to use a single study from the Basque region of Spain that found a huge increase in IQ as a centerpiece of its argument that there was too much uncertainty to conclude fluoridated water was neurotoxic. Extensive testimony was obtained from both sides about this study, including almost two hours of deposition from the lead author of the Basque study, Jesus Ibarluzea. Tellingly, despite originally intended by EPA to be a star witness, Ibarluzea withdrew from the case before the trial, which may have further reduced the credibility of his study in the court’s eyes.
The court ruling addressed the Ibarluzea study in depth and agreed it had many of the problems that had been pointed out during trial testimony. The court’s ruling said:
“The reliability of Ibarluzea (2021) is questionable in several respects: ... [followed by 2 pages of detailed reasons why the court considered the Ibarluzea study of questionable reliability; Court ruling, pp. 27-29]
… as also explained previously, particular characteristics of these studies finding null outcomes render them less probative here.... Ibarluzea (2021) found an unrealistic 15-point IQ benefit, included unexplained and implausible results regarding creatinine adjustments, and failed to control for seafood [Court ruling, p. 39]
This video is available to help those wishing to understand why the court agreed that the Ibarluzea study deserved little weight. Debunked: Study Finding Huge Increase In IQ From Fluoride Exposure Is Biologically Impossible](https://i.ytimg.com/vi/KU-XtSv3kqg/mqdefault.jpg)


