Fluoride and the endocrine system

Even before the US National Research Council found that extremely low levels of fluoride have the ability to affect our thyroid gland, there was plenty of evidence to show fluoride’s potential damage. Since then the evidence has only continued to grow.

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“We found that higher levels of fluoride in drinking water provide a useful contribution for predicting prevalence of hypothyroidism. We found that in areas of high fluoridation, i.e. more than 0.7mg/L, residents are nearly twice as likely to report high hypothyroidism prevalence in comparison to non-fluoridated area."
Dr. Stephen Peckham
BSc (Hons), MA, Professor of Health Policy at the University of Kent and the London School of Hygiene and Tropical Medicine, UK.
  • The endocrine system plays an integral role in our health and development;
  • There is a long-recognised association between fluoride and the thyroid dysfunction;
  • Iodine deficiency lowers the threshold at which fluoride damages the brain, interferes with thyroid functioning and other forms of fluoride toxicity;
  • This iodine relationship is all the more significant in Australia where natural iodine levels are low;
  • According to ATF, more than 50% of children and pregnant breastfeeding women in Australia are iodine deficient;
  • Iodine uptake is further reduced by fluoride;
  • NHMRC DOUBLES upper levels for children up to age 8;
  • US NRC review (2006)  found effects on thyroid function were associated with extremely low levels of fluoride  when iodine intake was adequate and even less when iodine intake was inadequate; THIS SHOULD BE OF MAJOR CONCERN FOR AUSTRALIA!;
  • Symptoms of hypothyroidism include depression, fatigue, weight gain, muscle and joint pains, increased cholesterol levels, and heart disease;
  • We review three major fluoride/thyroid studies since NHMRC’s cut-off date for the last fluoridation review and ask how all three studies can be dismissed or ignored?
  • Also see other recent thyroid studies here.
The endocrine system

The endocrine system is a chemical messenger system consisting of a number of glands that secrete a variety of specific hormones directly into the circulatory system to regulate the function of organs and the body’s metabolism, growth and development, tissue function, sexual function, reproduction, sleep, mood and other more subtle physiological functions.

Two of the most important glands in this system are the thyroid and adrenal glands. The thyroid gland secretes three hormones called T3, T4 and calcitonin. The thyroid itself is regulated by thyroid-stimulating hormone (TSH) secreted from the pituitary gland, which in turn is regulated by the hypothalamus. TSH is referred to as the master hormone or the “first violinist in the endocrine orchestra”.

The endocrine system is therefore a rather complex interrelated system that plays an enormously important role in our overall health and development.

Fluoride and the thyroid

There is a long-recognised association between the potential effects of fluoride and the thyroid gland, dating back to 1854 when French chemist Edme-Jules Maumené first linked goitre – a thyroid condition – in dogs exposed to fluoride. A detailed chronology of research examining the fluoride-thyroid link, along with various references, can be found here.

These studies have shown that fluorides act like, and may in some ways imitate, THS. During the 1980s and 1990s, as the science of molecular biology developed, many studies revealed a more subtle influence of fluoride on G-proteins, which are stimulated by TSH and act as “on and off switches” for cellular signal transmission. It was in the late 1990s that fluorides became known as the universal G-protein activator.

In fact in the past, sodium fluoride was used to treat patients suffering from hyperthyroidism (over-active thyroid). In the 1920s and 1950s, doctors prescribed between 2mg and 5mg per day to treat this condition – a dose well within the average Australian’s estimated total daily dose of fluoride ingested from all sources. Therefore it is only logical that fluoride has the potential to supress or reduce the activity of a normal or already underactive thyroid – increasing the likelihood of or directly causing hypothyroidism (under-active thyroid). That’s exactly what many studies have revealed.

It is also important at this point to mention the significance of iodine, which is the basic building block of the T3 and T4 hormones. An adequate iodine intake is essential for the proper functioning of the thyroid gland. When iodine intake is inadequate during infancy and early childhood, the child’s brain can suffer permanent damage, including mental retardation. In fact iodine deficiency is a leading cause of mental retardation worldwide. Several research studies also show that fluoride exposure worsens the impact of an iodine deficiency.

In China alone, researchers have repeatedly found that an iodine deficiency coupled with fluoride exposure produces a significantly more damaging effect on neurological development than iodine deficiency alone. The studies showed that an iodine deficiency lowers the threshold at which fluoride damages the brain along with other forms of fluoride toxicity, including dental fluorosis.

This iodine relationship is particularly relevant to Australia and New Zealand where iodine deficiency can be a serious problem. The Australian Thyroid Foundation, a leading education and advocacy organisation on thyroid health provides this relevant information:

“In continents such as Australia and New Zealand, natural iodine levels are very low in the soils where we grow our vegetables, grains and graze livestock. Insufficient iodine in the diet results in a range of conditions known as Iodine Deficiency Disorder (IDD). Iodine deficiency is becoming an increasingly common cause of thyroid health problems in Australia.

"Iodine Deficiency raises important health concerns with pregnant and lactating women and the developing baby."

"Iodine deficiency is becoming an increasingly common cause of thyroid health problems in Australia."

"More than 50% of children and pregnant or breastfeeding women living in Australia have been shown to be iodine deficient, and are at risk of developing thyroid disease."

Australian Thyroid Foundation

There is also evidence to show that iodine uptake is reduced by fluoride. In March 2019, Environmental Scientist Declan Waugh, published a study 1 on the effect of fluoride on iodine absorption.  “Based on the findings of this study, evidence strongly suggests that F ingestion contributes to pathological states by impairing iodine absorption and diminishing iodine concentrating ability,” Waugh concluded.

Thyroid and bottle-fed babies

It is also of particular concern that bottle fed babies are ingesting a dose of fluoride that is associated with an effect on the thyroid, even when iodine intake is adequate and even before considering the neurotoxic effects of fluoride. To make matters worse, Australia’s National Health and Medical Council (NHMRC) and FSANZ doubled the upper levels for allowable reference doses of fluoride for infants and children up to 8 years of age. For more details, read our article, Fluoride and our young.

The NRC Review

In 2006 the prestigious US National Research Council (NRC), a division of the National Academies of Science which is funded by the US Public Health Service, published the results of the most comprehensive review of the scientific literature on fluoride ever undertaken. A 12-member panel took three years to review all the known science.

In their 517-page publication, Fluoride in Drinking Water, they examine in detail the dose of fluoride that might affect the thyroid.  They found that in humans, effects on thyroid function were associated with extremely low levels of fluoride of 0.05-0.13 mg/kg/day when iodine intake was adequate and 0.01-0.03 mg/kg/day when iodine intake was inadequate. This is of major concern given that these levels are well below average total daily dose of fluoride for Australians. It is also remarkable, considering the rampant and increasing rates of hypothyroidism in several major fluoridated countries. Symptoms of hypothyroidism include depression, fatigue, weight gain, muscle and joint pains, increased cholesterol levels, and heart disease.

In 2010, Synthroid (sodium levothyroxine), a hormone replacement drug used to treat an underactive thyroid, was ranked as the fourth most prescribed medication in the United States. In 2018 it was the top prescribed medication.

Several crucial statements were made by the NRC review, as follows:

“In summary, evidence of several types indicates that fluoride affects normal endocrine function or response; the effects of the fluoride-induced changes vary in degree and kind in different individuals. Fluoride is therefore an endocrine disruptor in the broad sense of altering normal endocrine function or response…”
“The effects of fluoride on various aspects of endocrine function should be examined further, particularly with respect to a possible role in the development of several diseases or mental states in the United States.”
 “Fluoride exposure in humans is associated with elevated TSH concentrations, increased goiter prevalence, and altered T4 and T3 concentrations; similar effects on T4 and T3 are reported in experimental animals..”
“In humans, effects on thyroid function were associated with fluoride exposures of 0.05-0.13 mg/kg/day when iodine intake was adequate and 0.01-0.03 mg/kg/day when iodine intake was inadequate.” p.262-3
 “Intake of nutrients such as calcium and iodine often is not reported in studies of fluoride effects. The effects of fluoride on thyroid function, for instance, might depend on whether iodine intake is low, adequate, or high, or whether dietary selenium is adequate.”

The NRC concluded that “several lines of information indicate an effect of fluoride exposure on thyroid function.” They also emphasised that further research was required.

Since the 2006 NRC review, further studies have found alterations in thyroid hormones, including reduced T3 and increased TSH, in populations exposed to elevated levels of fluoride in the workplace or in the water.

"Several lines of information indicate an effect of fluoride exposure on thyroid function."

US National Research Council; "Fluoride in Drinking water" 2006 Review
The Peckham study

In February 2015, British scientists at the University of Kent reported that fluoridated water in Britain is associated with elevated rates of hypothyroidism. The study, published online February 24 in the Journal of Epidemiology and Community Health, describes the first population-level study investigating the association between fluoride levels in drinking water and hypothyroidism.

The study’s lead author, Stephen Peckham, BSc, MA, a professor of health policy at the University of Kent and the London School of Hygiene and Tropical Medicine in the UK, summarises as follows:

“We found that higher levels of fluoride in drinking water provide a useful contribution for predicting prevalence of hypothyroidism. We found that in areas of high fluoridation, i.e. more than 0.7mg/L, residents are nearly twice as likely to report high hypothyroidism prevalence in comparison to non-fluoridated area,” says Dr. Peckham.

This study was criticised, mainly for its lack of control for some confounding factors, however Dr Peckham stands by his findings: “Some of the conclusions might be overstated, but I don’t think that makes a difference to the actual analysis,” said Dr Peckham. “Criticisms that this was an ecological study were also unusual given that ecological studies using published data are widely used to compare factors in public health and environmental research,” he said.

Dr Peckham highlighted the study’s weaknesses:

  • It showed an association between fluoride levels and hypothyroidism, not direct causation
  • There was no individual data available on thyroid function, fluoride ingestion, fluoride exposure or iodine levels;
  • It was not possible to identify all fluoride sources;
  • The length of residence in an area was unknown, however the movement of people between practices is small;
  • The study could not necessarily align practice areas with fluoridated areas.

Nevertheless, he emphasised the study’s strengths:

  • The study was substantial, including the health records of 55 million people across 7,900 data points (or medical practices) – a stark comparison to most dental surveys in the UK that normally use around 150 data points;
  • The study involved good quality population data based on registered medical practice population;
  • Accurate levels of fluoridation levels were included rather than assuming 1ppm for the whole of the fluoridated area;
  • While it didn’t control for all confounding factors it did adjust for the major confounders of sex, age and iodine in food consumed from the National Diet Survey.

Also the study only looked at hypothyroidism rather than other subclinical thyroid effects so the results might actually be conservative.

With such a large number of health records, this study has identified a red flag or an association that requires further investigation rather than being dismissed for its weaknesses. “The evidence for a benefit is not strong enough to support community water fluoridation, and the evidence for harm is not weak enough to be dismissed”, said Dr. Peckham.

But that’s exactly what NHMRC did – dismissed the Peckham study, claiming that it was “unreliable evidence” and they failed to investigate this matter further as any responsible national health body would have done. This dismissal occurred despite full awareness of the potential damage to the thyroid as acknowledged in the 2006 US National Research Council report “Fluoride in Drinking Water”, as mentioned above.

"We found that in areas of high fluoridation, i.e. more than 0.7mg/L, residents are nearly twice as likely to report high hypothyroidism prevalence in comparison to non-fluoridated area."
Stephen Peckham
BSc (Hons), MA, Professor of Health Policy at the University of Kent and the London School of Hygiene and Tropical Medicine, UK.
The Kheradpisheh study

In February 2018, the results of another study again showing that fluoridation can damage the thyroid gland were published in Nature magazine. Titled, “Impact of Drinking Water Fluoride on Human Thyroid Hormones: A Case- Control Study” (Kheradpisheh et al. 2018) , this case-controlled study found that fluoride impacts human thyroid hormones, especially TSH and T3, even at concentrations of less than 0.5 mg/L – below Australia’s recommended range of 0.6 to 1.1mg/litre.

“The major finding of this study is that TSH values are higher with a higher fluoride concentration in the drinking water, even for generally low fluoride concentrations. This is seen both in cases of untreated hypothyroidism and in controls.”

“Some studies have discovered the relation between dental fluorosis and thyroid disease,” write Kheradpisheh’s team.

Many studies have found that fluoride can affect the thyroid gland.
The Malin study

In October 2018, the results of this study were published in Environment International. Titled “Fluoride Exposure and Thyroid Function Among Adults Living in Canada: Effect modification by iodine status” (Malin A.J. et al 2018), this study is particularly relevant to Australia because it showed that Canadian adults who are iodine deficient and have higher fluoride exposure are at an increased risk of hypothyroidism.

“While our findings only establish an association, not cause-and-effect, they are important because they suggest a potential effect of fluoride on thyroid function at levels of exposure that are typical for Canadians,” said Christine Till, the study’s senior author and associate professor at York University.

The study used population-based data from a Canadian Health Measures Survey (CHMS) consisting of 6.9 million adults between the ages of 18 and 79 years. Adults who were diagnosed with a thyroid disorder, or who were on thyroid medication, as well as pregnant women, were excluded.

The research team, based out of York University in Toronto, and the Department of Environmental Medicine and Public Health, Icahn School of Medicine at Mount Sinai in New York, tested whether higher levels of fluoride in urine are associated with disrupted thyroid function in adults living in Canada.

"I have grave concerns about the health effects of fluoride exposure. And not just from my study but the other studies that have come out in recent years."
Ashley Malin
Lead author and post-doctoral fellow at the Department of Environmental Medicine and Public Health, Icahn School of Medicine at Mount Sinai in New York.

The study found that adults who are iodine deficient and have higher levels of fluoride in their system have a greater risk of an underactive thyroid. In fact 18 per cent of the 6.9 million adults they studied were iodine deficient. That’s potentially around 1.2 million people at risk of an underactive thyroid due to fluoride exposure.

“Prior studies investigating fluoride exposure and thyroid function among adults did not consider iodine status – an important modifying factor,” said lead author, Ashley Malin, post-doctoral fellow at the Department of Environmental Medicine and Public Health, Icahn School of Medicine at Mount Sinai in New York. “It was particularly important that we considered iodine status in this study because iodine deficiency is relatively common among adults in Canada.”

“Fluoride may interfere with enzymes that contribute to thyroid hormone synthesis and active transport of iodine into the thyroid,” Malin said. “Iodine may also facilitate bodily excretion of fluoride, thereby buffering the thyroid from its potential adverse effects.”

“I have grave concerns about the health effects of fluoride exposure,” Malin said. “And not just from my study but the other studies that have come out in recent years.”

Conclusion

Hundreds of research studies indicate that fluoride has the potential to damage the thyroid gland and contribute to a clinical (diagnosed) or subclinical (undiagnosed) hypothyroid condition.  So when the US NRC’s comprehensive review found that a tiny fraction of the fluoride concentration found in Australia’s drinking water could adversely affect the thyroid, these results should have set alarm bells ringing and triggered further investigation by Australia’s national health body.

Instead, these findings were ignored and the next significant study by Peckham et al, published in 2015, were flippantly dismissed despite the enormous size of the study, the quality of data, the controls used and the standard methodology employed. Once again NHMRC refused to investigate this matter further, arrogantly claiming that fluoridation is safe.

Since NHMRC’s latest fluoridation review was released in 2017 (Information Paper – Water fluoridation: dental and other human health outcomes, NHMRC, July 2017), the findings of the Kheradpisheh and Malin studies have been published, again providing serious warnings to our health authorities. So far these warnings have continued to be ignored.

With all this evidence, especially considering the Peckham, Kheradpisheh and Malin studies, suggesting that many Australians with an iodine deficiency may be more susceptible to hypothyroidism, and with the rampant increase in hypothyroid conditions in Australia, it is remarkable that Australia’s NHMRC has not made any effort to conduct any research to investigate this matter further and meanwhile continues to repeat its claim that fluoridated drinking water causes “no harm”.

As Paul Connett, PhD, James Beck MD, PhD and Henry Micklem DPhil, say in their book, The Case Against Fluoride; “When one considers the millions of people affected by hypothyroidism (underactive thyroid) in fluoridated countries and the millions more probably suffering from subclinical (undiagnosed) hypothyroidism, the omissions in many government-sponsored reviews are unfathomable.”

With public water fluoridation, we are forcing people to drink a possible thyroid-depressing medication that could cause higher levels of both subclinical and clinical hypothyroidism in the general population, with all the attendant problems such as depression, fatigue, weight gain, muscle and join pain, increased cholesterol levels, and heart disease, as well as cognitive dysfunction and damage to the developing brain.”

Paul Connett, PhD, James Beck MD, PhD and Henry Micklem DPhil, "The Case Against Fluoride" Tweet

Notes

  1. “Fluoride Exposure Induces Inhibition of Sodium/Iodide Symporter (NIS) Contributing to Impaired Iodine Absorption and Iodine Deficiency: Molecular Mechanisms of Inhibition and Implications for Public Health.” Declan T. Waugh, March 2019.