- Shaik N, Shanbhog R, Nandlal B, Tippeswamy HM - "Fluoride ingestion and thyroid function in children resident of naturally fluoridated areas - An observational study" J Clin Exp Dent 11(10):e883-e889 (2019) doi: 10.4317/jced.55812. PMID: 31636857; PMCID: PMC6797461
- NOTE: This work was published in two different journals - the second publication is:
Shaik N, Shanbhog R, Nandlal B, Tippeswamy HM - "Fluoride and Thyroid Function in Children Resident of Naturally Fluoridated Areas Consuming Different Levels of Fluoride in Drinking Water: An Observational Study"
Contemp Clin Dent 10(1):24-30 (2019) doi: 10.4103/ccd.ccd_108_18
There are many things wrong with this study, from determination of F- in water/serum levels, to the gender make-up of study groups. No indication is given if free or total thyroid hormones were measured. From the figures, it appears that total fractions were measured, not FT3 and FT4. Serum fluoride levels indicate that there are other sources of fluoride. It is therefore not surprising that children in the area with the lowest fluoride water concentration already have increased mean TSH levels compared to other recent investigations, and that the occurrence of dental fluorosis rises with an increase in T3 levels. 88 % of children have dental fluorosis in the area with 1.44 ppm fluoride in the water.
However, in spite of all the flaws in this study, the author's ignorance of thyroid hormone metabolism is what ultimately proves the study's downfall.
Shaik et al. claim that fluoride in water at the levels used in this study (0.02 -1.4 ppm) does not cause any changes in thyroid hormones. Based on the data presented this conclusion is incorrect.
An increase in the T3/T4 ratio is clearly seen between the no/low fluoride area (Group 1) compared to the two higher ones.
- T3/T4 Ratio:
Group 1: 14.69
Group 2: 17.84
Group 3: 17.04
Table: https://poisonfluoride.com/Science/NTP_ ... k_2019.png
Pedraza PE, Obregon MJ, Escobar-Morreale HF, del Rey FE, de Escobar GM - "Mechanisms of adaptation to iodine deficiency in rats: thyroid status is tissue specific. Its relevance for man" Endocrinology 147(5):2098-108 (2006)