Shashi A, Singla S - "Syndrome of Low Triiodothyroinine in Chronic Fluorosis" International Journal of Basic and Applied Medical Sciences 3(1):152-160 (2013)
The present study examined the thyroid function and low T3 state in a group of patients exposed to different concentration of fluoride in drinking water. 139 subjects from severe endemic fluorosis areas and 140 subjects as control group were randomly selected. The functional activity of thyroid gland was measured and the findings indicate that the level of TSH and rT3 was significantly (P<0.001) elevated and of T3 was declined in the fluorotic group. The T4 concentration showed significant (P<0.05) elevation in A-III and A-IV groups, however the elevation in A-I and A-II was not statistically significant.
The level of fluoride (F) in serum and urine was significantly (P<0.001) higher in fluorotic study groups as compared to control group. Pearson’s bivariate coefficient of correlation revealed a positive relationship between water F vs. TSH (r= 0.98), water F vs. rT3 (r= 0.77) in different study groups. An inverse correlation existed between serum F vs. T3 (= -0.82) and serum F vs. T4 (r= -0.88). The study demonstrate that abnormalities in thyroid function characterized by a low level of T3, high rT3 and a slight increase of the TSH with normal to low T4 indicating low T3 syndrome in cases of chronic fluoride
intoxication. It is also evidenced that fluoride in excess may be inducing disease normally attributed to iodine deficiency. The normal or optimal levels of iodine in the urine and the low level of T3 with higher level of rT3 can serve as a diagnostic sign of chronic fluoride exposure.