Hosur et al., 2012 - Comments

All adverse health effects of fluoride are related to thyroid hormone metabolism.
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Hosur et al., 2012 - Comments

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  • Hosur MB, Puranik RS, Vanaki S, Puranik SR - "Study of thyroid hormones free triiodothyronine (FT3), free thyroxine (FT4) and thyroid stimulating hormone (TSH) in subjects with dental fluorosis" Eur J Dent 6 (2):184-90 (2012)
Hormones investigated: FT4, FT3, TSH

This study was conducted by dental professionals from the P.M.N.M Dental College and Hospital, Bagalkot, Karnataka, INDIA.

It is another one of a series of studies seemingly undertaken to disprove earlier findings that fluoride caused disturbances in thyroid hormone metabolism.

Background of the Study

In 2005, Susheela et al. had reported on their study in India which, for the first time, investigated the free thyroid hormones FT4 and FT3, as well as TSH, in children with dental fluorosis (DF), 7 to 18 years old. There were two control groups and one study group. Susheela et al. had found that there were thyroid disturbances in all groups - and that the disturbances were related to the fluoride serum/urine levels. They realized that in all groups it was total fluoride intake that mattered, not just the fluoride in the water supply. They further observed that the variation in thyroid disturbances resembled those normally seen in iodine deficiency disorders.
  • SIDEBAR: DF can only occur from fluoride exposure during crucial times of development - in utero to about 30 months of age for deciduous teeth and permanent incisors - esthetically the most important teeth. The dental defects seen in DF stem from thyroid hormone disturbances that occurred during that particular time period, when thyroid hormone activity is vastly different than in later years. The permanent incisors themselves don't erupt until about age 7. When thyroid hormones are measured they can only reflect the thyroid status at the time of the investigation. Likewise, when fluoride is measured in serum/urine, it reflects current intake. The children here are between 10 and 18 years old.

Hosur et al. summarized correctly:

"A recent study by Susheela et al. on children with dental fluorosis living in National Capital Territory of Delhi has shown that these children have well-defined thyroid hormone derangements, similar to those observed in subjects with iodine deficiency disorders. Even children without DF, but with elevated serum fluoride levels, exhibited similar hormonal derangements."

So - it can be presumed that Hosur et al. were in full knowledge of the findings by Susheela et al., regarding the importance of total intake and the need to compare serum/urine levels of fluoride with TSH and thyroid hormones. It also must be presumed that they knew and understood what these "well-defined thyroid hormone derangements" were.

Yet they continued in the study design as if this knowledge did not exist.

Hosur et al. took 65 children 10-18 years who had dental fluorosis and compared thyroid hormone levels in that group to those in a small control group of children who were 12-14 years old, and did not have the condition.

They did NOT investigate thyroid hormone levels and compared to fluoride concentrations in the water, as Susheela et al. did.

They also did NOT evaluate any fluoride levels in serum/urine, as Susheela et al. did.

When Hosur et al. investigated the severity of dental fluorosis in relation to thyroid hormones, they found significant alterations in FT3 and TSH with the degree of DF.

Yet, in their conclusion they wrote that no "significant alterations were observed in children with dental fluorosis." They proclaimed the opposite to what their own data actually revealed. It is this conclusion that is stated when this paper is cited by others eager to distort fluoride effects on thyroid hormones, such as Barberio et al. (2017), or Shaik et al. (2019). The actual data in the paper tells an entirely different story.

Let's look at a few of the questionable aspects of this study.

Control Group

The control group is not a control, as far as fluoride levels in water are concerned.

A large portion of the control group may have had more fluoride in the water than the study group. The control children came from "safe" areas of < 1 ppm. Details are not presented.

On the other hand, in the DF group: "There were total 42 dental fluorosis subjects who consumed water with fluoride levels of 0.5–0.6 ppm in our study."

In other words - 62 % of study children may have had less F- in water than the control, but had moderate and severe dental fluorosis (there were only 4 cases of mild dental fluorosis). Please note that the concentration of 0.5-0.6 ppm is BELOW the level commonly used in "Community Water Fluoridation" (0.7 ppm).

As both groups had largely similar water fluoride levels, both groups also displayed largely similar disturbances in thyroid hormone metabolism.

What did the study find?

Despite the author's conclusions the data reveals some valuable information.

"FT3 levels were significantly different between mild and moderate, as well as between mild and severe fluorosis groups...a significant difference was found between TSH levels of moderate and severe fluorosis groups."

  • Table Hosur:


    (When looking at the table, be aware that the data for the "mild" category comes from only 4 children, as opposed to 33 in the moderate group, and 28 in the severe group.)
In the table a clear increase in TSH levels with increasing severity of DF is observed. Again, the TSH level in the severe DF group is above the upper limit of the 1st trimester threshold for pregnant women (2.5 mIU/L) - including in subjects consuming water at 0.5 to 0.6 ppm fluoride.

When the very small minority of 4 children with mild DF is excluded, the difference is quite apparent:

Moderate DF: 1.96 | Severe DF: 2.58

Moderate DF: 3.05 | Severe DF: 3.18

Mean FT3/FT4 Ratio:

Moderate DF: 2.99. Severe DF: 3.18

More about the Control group/Age:

The control group (12-14 years) are mainly children at the age of puberty when TSH, FT4 and FT3 levels change in girls vs boys (Kaloumenou et al., 2010; Kratsch et al., 2008). 9 of the 10 children are 12 or 13 years old. This further distorts the true extent of fluoride effects.

see Table 3: https://www.poisonfluoride.com/Science/ ... able_3.png

"Normal Range"

Hosur et al. conclude:

"However, this study showed that 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. These findings are in contradiction with the findings of Susheela et al. Also in our study, 1 individual in the control (non-fluorosis) group showed an elevated TSH level, which seems to have been a chance finding. Thus, it appears that thyroid hormone levels were not affected in dental fluorosis patients."

When compared to the Susheela data, both studies show similar derangements in thyroid hormones. There is no contradiction at all. Hosur et al. just used a different TSH "normal range" for their false conclusions. There is no real understanding on ratios or matters related to thyroid dysfunction. There is no understanding of the "well-defined thyroid hormone derangements" mentioned earlier. Fortunately for the reader, Hosur et al. provide individual data for all 65 cases. When these values are investigated in detail, the very same disturbances as reported by Susheela et al. are clearly visible - for both groups, as is to be expected if both areas had similar levels of fluoride intake.

Here as well - as was observed by Susheela et al. - there are obviously other sources of fluoride, as moderate and severe dental fluorosis was occurring at concentrations of 0.5 to 0.6 ppm in the water. The dental fluorosis severity is similar to that observed in iodine deficiency (Lin et al., 1991,1992; Zhao et al., 1998).

Coming back briefly to the DF/thyroid hormone findings:
"FT3 levels were significantly different between mild and moderate, as well as between mild and severe fluorosis groups."
This points to disturbances in deiodination, as FT4 levels are similar in all DF groups. (No mean levels are supplied for control children, only minimum and maximum values.)

The associations of mild, moderate and severe DF with TSH and FT3, as doumented here by Hosur et al., are similar to those found by Zhao et al. in mice. The extensive 10-year long investigation by Zhao and his team on the effects of fluoride on DF in various thyroid states is still the most extensive research done in animals on this subject. It is quintessential information. It clearly shows how the severity of DF is related to both fluoride and iodine (Zhao et al., 1998, 1992, 1988).

Hosur et al.:

"Unfortunately, statistical comparison of thyroid hormone levels between the study and control groups was prevented by the small sample size of the control group."

"Serum fluoride levels may be the best indicator of fluoride toxicity. However, due to practical difficulties, it was not possible for us to analyze serum F− levels of study or control individuals."

Major shortcomings, as discussed above. Then the conclusion: despite the significances reported in FT3 and TSH values compared with the DF index the authors conclude - quite unbelievably - as follows:
"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.
The authors are stating the opposite of their actual findings. There was obviously another agenda.

Hosur et al.:

"Fluoride toxicity remains a controversial subject, because several animal and human studies have shown conflicting results."


"The relationship between fluoride intoxication and thyroid function is highly debatable."

These are statements commonly found in pro-fluoridation literature. Is there really a controversy? Is it debatable?


Out of the 400 studies that have been conducted on the subject in the last 40 years, at least 95% document adverse effects of fluoride upon thyroid hormone metabolism.

Hardly a controversy. The evidence is quite overwhelming.

The very few that don't are very questionable studies such as the present one, and all done by people who are closely tied to pro-fluoridation measures (i.e. Leone 1964, Baum 1981, Demole, 1970 - all cited here.)
  • NOTE: Hosur et al. do not cite references appropriately. For example, for Leone (1964) and Baum (1981) they use the 2006 NRC review as source. For Demole's fraudulent WHO review from 1970 they cite a study by Zhan on pigs in 2006. For Yu (1985) a paper by Trabelsi is given as reference. One wonders if they ever read the original papers they are referring to? Was this paper ever peer-reviewed?
Wendy Small,
PFPC 2020


Kaloumenou I, Duntas LH, Alevizaki M, Mantzou E, Chiotis D, Mengreli C, Papassotiriou I, Mastorakos G, Dacou-Voutetakis C - "Gender, age, puberty, and BMI related changes of TSH and thyroid hormones in schoolchildren living in a long-standing iodine replete area" Horm Metab Res 42(4):285-9 (2010)

Kratzsch J, Schubert G, Pulzer F, Pfaeffle R, Koerner A, Dietz A, Rauh M, Kiess W, Thiery J - "Reference intervals for TSH and thyroid hormones are mainly affected by age, body mass index and number of blood leucocytes, but hardly by gender and thyroid autoantibodies during the first decades of life" Clin Biochem 41(13):1091-8 (2008)

Susheela AK, Bhatnagar M, Vig K, Mondal AK - "Excess fluoride ingestion and thyroid hormone derangements in children living in Delhi, India" Fluoride 38(2):151-161 (2005)

Zhao W, Zhu H, Yu Z, Aoki K, Misumi J, Zhang X - "Long-term Effects of Various Iodine and Fluorine Doses on the Thyroid and Fluorosis in Mice" Endocr Regul 32 (2):63-70 (1998)

Zhao WY, Zhu HM, Gao YZ, Qin L, Chen CY, Xu DQ - "The study of combined iodine and fluorine activity on experimental goiter and fluorosis" J Chinese Endemic Diseases, Prevention and Treatment (7):16-18 (1992)

Zhao WY - "A preliminary study of the interaction of iodide and fluoride in experimental iodide-goiter and fluorosis" Chung Hua Yu Fang I Hsueh Tsa Chih 22(3):146-8 (1988)
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Susheela et al., 2005

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Susheela AK, Bhatnagar M, Vig K, Mondal AK - "Excess fluoride ingestion and thyroid hormone derangements in children living in Delhi, India"
Fluoride 38(2):151-161 (2005)
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.
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Singh 2014

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Singh N, Verma KG, Verma P, Sidhu GK, Sachdeva S - "A comparative study of fluoride ingestion levels, serum thyroid hormone & TSH level derangements, dental fluorosis status among school children from endemic and non-endemic fluorosis areas" Springerplus 3:7 (2014) doi: 10.1186/2193-1801-3-7. PMID: 24455464; PMCID: PMC3890436

"The serum and urine fluoride levels were found to be increased in both the groups. A significant relationship of water fluoride to urine and serum fluoride concentration was seen. The serum fluoride concentration also had a significant relationship with thyroid hormone (FT3/FT4) and TSH concentrations."
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