Study of thyroid hormones free triiodothyronine (FT3), free thyroxine (FT4) and thyroid stimulating hormone (TSH) in subjects with dental fluorosis

Abstract

Objective:Apart from its well-known deleterious dental and skeletal effects, fluoride excess can have toxic effects on many other tissues. Fluoride, when in excess, is known to interfere with thyroid gland function. Fluoride-induced thyroid disturbances similar to those observed in iodine deficiency state in spite of adequate iodine intake have been documented. Similar thyroid disturbances in individuals with dental fluorosis have not been well studied in populations with endemic fluorosis. This work was undertaken to study the effects of fluoride-induced thyroid disturbances in individuals with dental fluorosis.Methods:The study group included 65 subjects with dental fluorosis from endemic fluorosis populations. An additional control group was comprised of 10 subjects without dental fluorosis. The drinking water fluoride levels of the study populations were analyzed. Serum free FT3, FT4, and TSH levels of both groups were assessed.Results:All subjects with dental fluorosis had serum levels of thyroid hormones (FT3, FT4, and TSH) within the normal range, with the exception of 1 individual, who had elevated levels of TSH. Statistical significance was found when FT3 and TSH values were compared with different Dean’s index groups by a 1-way ANOVA test: FT3 (F = 3.4572; P=.0377) and TSH (F = 3.2649 and P=.0449).Conclusions:Findings of this study did not show any significant alterations in the levels of the thyroid hormones FT3, FT4, and TSH in subjects with dental fluorosis. Our observations suggest that thyroid hormone levels were not altered in subjects with dental fluorosis. Hence, future studies of this kind, along with more detailed investigations are needed.

Dental caries prevalence and its association with fluoride level in drinking water in Sana’a, Yemen

“…[ 11 17 22 ] All in all, the balance between the achievement of maximum protection against dental caries and the risk of development of fluorosis should be taken into consideration. [ 25 ]…”

Fluoride exposure and indicators of thyroid functioning in the Canadian population: implications for community water fluoridation

“…For example, Michael et al (1996) 5 found no difference in the levels of thyroid-stimulating hormone (TSH) between those with low and high fluoride exposure (fluoride exposure was not clearly defined), whereas Lin et al (1991) 8 found that individuals residing in high fluoride areas (defined as areas with an average fluoride concentration of 0.88 parts per million (ppm) in drinking water) had significantly higher TSH levels than those residing in low fluoride areas (average fluoride concentration of 0.34 ppm in drinking water) (p<0.01). Conversely, a study by Hosur et al (2012) 9 did not detect altered levels of thyroid hormones (free T3, free T4 and TSH) in 65 individuals living in India with dental fluorosis (used as a proxy for high fluoride exposure), with the exception of one individual whose serum levels of TSH were elevated. The results of these small-scale human studies should be interpreted with caution in light of limited details regarding the study sample, unclear descriptions of fluoride exposure classification and lack of adjustment for other important covariates (eg, iodine status).…”

Fluoride, Thyroid Hormone Derangements and its Correlation with Tooth Eruption Pattern Among the Pediatric Population from Endemic and Non-endemic Fluorosis Areas

“…Among subjects with dental fluorosis, they didn't observe any significant alteration in the thyroid hormone levels. 13 For the assessment of the severity of dental fluorosis, along with thyroid function and bone metabolic indicators among school children, Khandare et al conducted a case-control study. They carried out the investigation in the area where drinking water was contaminated, and heat stressed.…”