Analysis on the Correlation Between TSH and Intelligence in Children with Dental Fluorosis from Endemic Fluorosis Regions.

Abstract

Fluoride is one of the indispensable elements for the living being. Excess amounts of fluoride, however, may damage the teeth and bones. Fluoride may also injure the body’s soft tissues, resulting in nonskeletal fluorosis. To further investigate the influence of endemic fluorosis on childhood thyroid function and intelligence, we have selected school-aged children inflicted with dental fluorosis as the subject of our study. These children are from a region impacted with endemic fluorosis: Chaoyang City of Liaoning Province. The children in the study were tested for TSH (Thyroid Stimulating Hormone) and intelligence, and meaningful results were found. The results are reported in the following text.

1. Subjects and Methods

1.1 Subjects School children between 8 to 12 years old, who were born in the affected area and are exposed to drinking water from source containing 2.0 mg/L and 11.0 mg/L of fluoride, have been tested. These children suffer from dental fluorosis but not from goiter, and are living in two neighboring villages, one which is slightly affected by a relatively low level of endemic fluorosis
and another with severe fluorosis. Another group of children were chosen as the control group. The control group lives in a non-endemic area with a source containing 1.0 mg/L of fluoride.

1.2 Methods

The TSH methods draws blood from the ear of the subject, which is then applied onto the filter paper. These items were supplied by the  TSH Quantatative Assay Kit (TMK-­433), and the filter paper was provided by the China Institute of Atomic Energy. The method used for this investigation was in compliance with the protocol set forth in the Assay kit…

3. Discussion

Both iodine deficiency and fluorosis can influence the level of intelligence [1-­3] in children. The TSH level is a sensitive index which both reflects the state of the body’s thyroid function, and screens the level of iodine (lack thereof) in a population. TSH is also a sensitive indicator in terms of making timely discoveries of people suffering from poor thyroid function or below-average intelligence. The results fromt his test show that TSH values of children with dental fluorosis from the two endemic areas is at a remarkably higher level than those from the non-endemic area. Children from the endemic areas were also found to have a lower level of intelligence than the non-endemic group. The heavier the level/concentration of fluoride found in the regio, the more significant the difference in the results. It leads one to wonder the cause to this result: Could it be the responsibility of iodine deficiency, or could it be a result of the high levels of fluoride found in the region? To answer this question, we focused this investigation on a geographical area that have reached the control standard for iodine deficiency thanks to a 27-year period of continuous iodine salt usage. thanks to a 27-year period of continuous iodine salt usage.

Currently, the daily intake of iodine of residents in the area is 329 ug/L, which exceeds the physiological demand (100-­200 ug/L). the daily intake of iodine of residents in the area is 329 ug/L, which exceeds the physiological demand (100-­200 ug/L)…

The mean value of urinary iodine was found to be 131.5 ug/L and measurements of T3 and T4 in the subjects’ serum were within the normal range. As per these results it is safe to conclude that the influence of Iodine deficiency on children can be removed as an explanation of the results in this study. In addition, the local economy, size of the schools, quality of teachers’  education, and the status of iodine nutrition are relatively the same in the exposed and control groups. This is particularly significant in the results from the two neighboring villages who were actually located in the same town (with one being the lightly endemic region and the other being the severely endemic region). The water fluoride level in the former village is 2.0 mg/L, while the water fluoride level in the later village is up to 11 mg/L. The severity of dental fluorosis from these two areas are deemed to be “serious” and “severe”, respectively, which reflects the fact that there is a comparable, yet different, degree of fluoride harm between these two endemic area groups. The results of the intelligence tests show that a high level of fluoride influences children’s IQ, which is consistent with some previous data[4].

It is worth mentioning that the higher the degree of dental fluorosis, the more negative the impact on the children’s intelligence level. This is an issue which merits utmost attention.

We believe that the low intelligence of children has no relation to the level of TSH. Although there are differences found in TSH values between the endemic area and non-endemic area  groups, and between the lightly endemic and severely endemic groups, the individual values are all within the normal range. The endemic and non­-endemic area groups are all control areas of iodine deficiency. Although the subjects were found to suffer from dental fluorosis, no thyroid goiter were found on them. The TSH value rises with the level of the fluoride epidemic are (from light to heavy degree) and is the result of interference by high fluoride. Further exploration on the influence or harm of this interference on the children’s body is required.

References

[1] Chen Zhihui, et al. Research on influencing factors on children’s intelligence development in iodine deficiency. Chinese Journal of Endemic Control, 1991; 6 (supplement):7

[2] Tan Yubin. The influence of fluoride on human metabolism and the various systems of the body. Chinese Journal of Endemic Control, 1994; 9(4):230.

[3] He Han, et al. Influence of fluoride on human’s fetus. Chinese Journal of Endemic Control, 1989; 4 fluoride (3):136.

[4] Qin Liansheng, et al. Inference and test  of the influence of the water fluoride on school-aged children’s intelligence with Revan  standard. Chinese Journal of Endemic Control, 1990;5 (4):203.

Accepted on: August 7, 1995.
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Translated from Chinese into English by FoxTranslate, courtesy of the Fluoride Acton Network (2012). For more transla9ons of Chinese research on fluoride toxicity, see http://www.fluoridealert.org/researchers/translations/