Ninety children with dental fluorosis, aged 7–18, living in fluoride endemic, non-iodine deficient areas of the National Capital Territory of Delhi, India, where iodized salt has been promoted for over a decade, were investigated, along with 21 children in two control groups without dental fluorosis living in nonendemic areas, to determine their levels of free T4 (FT4), free T3 (FT3), and thyroid stimulating hormone (TSH). The drinking water fluoride of the 90 children in the sample group ranged from 1.1 to 14.3 mg F–/L (mean 4.37 mg F–/L); their serum ranged from 0.02 to 0.41 mg F–/L (mean 0.14 mg F–/L); their urine ranged from 0.41 to 12.8 mg F–/L (mean 3.96 mg F–/L).
The drinking water fluoride of the control 1 group (n = 10) ranged from 0.14 to 0.81 mg F–/L (mean 0.23 mg F–/L) and that of the control II group (n = 11) ranged from 0.14 to 0.73 mg F–/L (mean 0.41 mg F–/L). In control I, only 3 children had serum fluoride below the normal upper limit of 0.02 mg F–/L. The remaining 7 children, even though they were consuming “safe” water, had elevated serum fluoride. In control II, only one child had serum fluoride below the normal upper limit. The remaining 8 children who were tested also had elevated serum fluoride. In control I, only 3 children had urine fluoride samples in the normal range (0.09–0.10 mg F–/L); in the remaining 7 children they were above normal. In control II, only one child had urinary and serum fluoride within the normal range. In the remaining 8 children who were tested it was high, suggesting they had excess F– exposure from sources other than drinking water.
The hormonal status of the 90 sample children indicated that 49 (54.4%) had well-defined hormonal derangements. In the remaining 41 children the findings were borderline. The hormonal deviations among the affected 49 children fall into the following five categories: (1) high TSH with normal FT4 and FT3 (46.9%); (2) normal TSH and FT4 with low FT3 (32.7%); (3) high TSH and FT3 with normal FT4 (14.3%); (4) high TSH with normal FT3 but low FT4 (4.1%); and (5) high TSH with normal FT4 but low FT3 (2.0%). In control I and control II, similar hormonal deviations were detected in as many as 50% and 45.4% of the children, respectively.
These findings indicate that children with or even without dental fluorosis from exposure to excess fluoride, either through drinking water or through other sources, may have thyroid hormone derangements that may not be clinically overt until late stages. Determining free T3, free T4, and TSH is therefore important for a proper diagnosis of potential health problems. Withdrawal from fluoride sources along with measures to correct the thyroid hormonal status may be necessary to promote better health in such children living in fluoride endemic areas.