Why Are So Many People Getting Thyroid Disease?

Estimates of the Frequency of Thyroid Disease Vary Widely

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One question thyroid patients frequently ask is "Why are so many people getting thyroid disease?" Let's take a look at the issue.

How Many People Have Thyroid Disease?

The first question is: how many people have thyroid disease? In the United States, there is a huge discrepancy among experts as to how many people have a thyroid condition. Some organizations cite 13 million as the total number of thyroid sufferers.

The American Thyroid Association says that 20 million Americans have thyroid conditions. According to the American Association of Clinical Endocrinologists, More recently, some groups estimate that 27 million Americans have thyroid disease, and about 13 million of them are undiagnosed.

The issue is further complicated by the controversy over the reference range for the Thyroid Stimulating Hormone (TSH) test. Since 2002, some groups have recommended narrowing the reference range from .5 - 5.0 to .3 to 3.0. If that narrower range were used, according to researchers:

"... using a TSH upper normal range of 5.0, approximately 5% of the population is hypothyroid. However, if the upper portion of the normal range was lowered to 3.0, approximately 20% of the population would be hypothyroid..."

That would mean that as many as 60 million Americans would fall outside the TSH reference range and as a result could conceivably be diagnosed with thyroid disease.

The Rise of Autoimmune Disease

One reason for increasing rates of thyroid disease is an increase in the prevalence of autoimmunity. In the majority of people with thyroid disease in the United States, an underlying autoimmune thyroid disease is causing their condition. Autoimmune diseases overall are definitely on the rise.

So it makes sense that with more autoimmunity, there will be an increase in thyroid disease as a result.

Increased Prevalence of Thyroid Cancer

Thyroid cancer is also on the rise. According to the American Cancer Society's most recent estimates, about 56,870 new cases of thyroid cancer (42,470 in women, and 14,400 in men) will be diagnosed in 2017, and there will be about 2,010 deaths from thyroid cancer (1,090 women and 920 men) in 2017. 

The chance of being diagnosed with thyroid cancer has risen in recent years and is now more than twice what it was in 1990. Some of this is the result of an increased use of thyroid ultrasound, which can detect smaller thyroid nodules that otherwise wouldn't have been found in the past. Still, at least part of the increase is from finding more large tumors as well.

Risk Factors for Thyroid Disease

What can be contributing to the rise in autoimmune-triggered thyroid conditions, other thyroid problems, and thyroid cancer? Experts have a number of theories, but no hard answers.

Chemicals and Toxins

We know that chemicals and toxins in the environment are linked to increased risk of thyroid disease. Some of the culprits include perchlorate, pesticides, phthalates like bisphenol-A (BPA), and thyroid-disrupting endocrine disruptors, also known as environmental estrogens.These chemicals are found in everything from non-stick pans, to plastic containers, to our water and food supply.


Radiation Exposure

Radiation exposure is also a risk factor that can trigger thyroid problems in some people. The radiation exposure that resulted from the Chernobyl disaster was a major trigger of thyroid disease, and experts have seen similar effects after Japan's Fukushima meltdown. You also face a higher risk of thyroid problems if you have had medical treatments involving radiation to your head and neck area, for example, treatment for Hodgkin's disease, nasal radium therapy, radiation to your tonsils and neck area. Even multiple dental x-rays have been linked to an increased risk of thyroid disease.


Viruses, bacteria, and pathogens can attack tissues and organs, triggering autoimmune diseases and inflammatory thyroid conditions. For example, there are links between Lyme disease, and Epstein-Barr/mononucleosis infections, and the onset of autoimmune thyroid disease. There is also a link between the foodborne bacteria Yersinia enterocolitica and an increased risk of thyroid disease.

Other Factors

Other controllable risk factors that may be responsible in part for increasing rates of thyroid disease include the following:

A Word from Verywell

Thyroid disease seems to be on the rise, with more people diagnosed with thyroid problems, and increasing rates of thyroid cancer. While a specific and single cause is not identifiable, there are a number of environmental and health factors that may be responsible for the increased prevalence of thyroid disease in the United States. 


American Cancer Society. Key Statistics for Thyroid Cancer. Online: https://www.cancer.org/cancer/thyroid-cancer/about/key-statistics.html Accessed July 12, 2017

American Thyroid Association. "General Information." Online: https://www.thyroid.org/media-main/about-hypothyroidism Accessed: July 12, 2017. 

Blackwell J. "Evaluation and treatment of hyperthyroidism and hypothyroidism." J Am Acad Nurse Pract. 2004 Oct;16(10):422-5.

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