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Thyroid Disease Far More Widespread Than Originally Thought, 13 Million May Be At Risk

March 05, 2000 | 31,771 views

A new study found that 13 million Americans may be unaware of and undiagnosed for their thyroid conditions and that more widespread thyroid testing is needed. This number is double the previously suspected level of undiagnosed cases in the United States. The study was funded by thyroid drug Synthroid's manufacturer, Knoll Pharmaceutical Co.

The study, known as the Colorado Thyroid Disease Prevalence Study, set out to determine how common abnormal thyroid function actually is, and to look at the relationship between abnormal thyroid function, cholesterol levels, and thyroid symptoms. The researchers studied 25,862 participants at the Colorado statewide health fair in 1995. Among patients not taking thyroid medication, 8.9 percent were hypothyroid and 1.1 percent were hyperthyroid. This indicates 9.9 percent of the population had a thyroid abnormality that had most likely gone unrecognized. These figures suggest that nationally, there may be 13 million Americans with an undiagnosed thyroid condition.

The study also found that even a slight decrease in thyroid function -- what is sometimes referred to as "subclinical" or low-level hypothyroidism -- may raise cholesterol levels. These findings are consistent with what was reported on by the American Association of Clinical Endocrinologists survey regarding cholesterol and thyroid disease in January of 2000. That study found that as many as ten percent of the 98 million Americans with high cholesterol levels may not know that their cholesterol is elevated due to undiagnosed thyroid problems.

The thyroid/heart disease/cholesterol linkage was further confirmed in the February 15, 2000 Annals of Internal Medicine's publication of the Rotterdam Study results. The Rotterdam study found that older women with subclinical hypothyroidism were almost twice as likely as women without this condition to have blockages in the aorta, and were also twice as likely to have had heart attacks.

The thyroid is a butterfly-shaped gland that wraps around the windpipe, behind the "Adam's Apple" area of the neck. The hormones produced by the gland are essential to stimulating metabolism, growth, and the body's capacity to process calories. An underactive thyroid -- hypothyroidism -- affects more women than men, and the risk increases with age for both men and women. The symptoms of hypothyroidism include fatigue, depression, weight gain, hair loss, muscle and joint pains, and many other chronic and debilitating symptoms. Low thyroid can also be linked to increased levels of LDL -- "bad" cholesterol -- and risk of heart disease.

The Colorado Thyroid Disease Prevalence Study found, not surprisingly, that as thyroid function declined, patients reported more symptoms such as hoarse voice, constipation, feeling tired, puffy eyes, muscle cramps, slower thinking, among others. But there wasn't a clear-cut linkage between the proportion and type of symptoms reported, and the level of thyroid failure, and no one individual symptom was a clear indicator of thyroid failure.

The link between all stages of hypothyroidism and cardiovascular health, and the vague correlation between symptoms and disease state, points to the need for more widespread thyroid stimulating hormone (TSH) testing and more aggressive treatment, especially for subclinical patients.

Is This Revised Estimate of 13 Million Still Too Low?

While the Colorado Study has effectively doubled the estimated percentage of the population believed to be suffering from undiagnosed hypothyroidism, some doctors believe that relying on the TSH normal range as the only way to define hypothyroidism may mean that still more millions are hypothyroid, but undiagnosed and overlooked due to rigid interpretation of bloodtest results and a need to reevaluate the TSH normal range.

The key thing is of course that what doctors are always told is that TSH is the test that gives us a yes or no answer. And, in fact, I think that's fundamentally wrong. The pituitary TSH is controlled not just by how much T4 and T3 is in circulation, but T4 is getting converted to T3 at the pituitary level. Excess T3 generated at the pituitary level can falsely suppress TSH.

Many people may be suffering from minute imbalances that have not yet resulted in abnormal blood tests. If we included people with low-grade hypothyroidism whose blood tests are normal, the frequency of hypothyroidism would no doubt exceed 10 percent of the population. What is of special concern, though, is that many people whose test results are dismissed as normal could continue to have symptoms of an underactive thyroid. Their moods, emotions, and overall well-being are affected by this imbalance, yet they are not receiving the care they need to get to the root of their problems....Even if the TSH level is in the lower segment of the normal range, a person may still be suffering from low-grade hypothyroidism.

What are the Implications for the Public?

This study, the largest to date that has looked at the prevalence of thyroid disease, has some important implications for the public.

The estimated 10% of the population -- double the number previous thought -- that is suffering from undiagnosed hypothyroidism points to an urgent need for doctors to become better educated about and more proactive in testing for thyroid disease. Patients also need to become more informed, and insist on thyroid testing when doctors or HMO's are reluctant.

The researchers felt that a careful evaluation of patients' symptoms should be an important part in the diagnosis of hypothyroidism, and the existence of several symptoms in tandem should be a signal to test for thyroid problems. This is a change in focus, in which doctors have indicated that most patients would not even experience symptoms at subclinically hypothyroid TSH levels. It is hoped that this realization that the symptoms -- and negative health consequences such as higher cholesterol -- of subclinical hypothyroidism warrant that the warning symptoms be taken more seriously, and not dismissed in the catchall "stressed, depressed, PMS'd or pre-menopausal" non-diagnosis that many thyroid patients have for years before they are actually diagnosed.

Among patients taking thyroid medication, only 60% were within the normal range of TSH. The fact that forty percent of patients, a number that translates to millions of Americans, are already taking thyroid hormone and being treated by a doctor but are still not in TSH range is of great concern. Not only does this show the need for more frequent monitoring and adjustment of dosages -- versus the typical doctor's recommendation of maximum yearly testing -- but may in fact suggest that there are serious inadequacies in the current therapies, which primarily almost solely on synthetic thyroid hormone replacement known as levothyroxine (brandnames Synthroid, Levoxyl, Levothyroid, Eltroxin).

The inadequacy of the standard therapy in relieving symptoms was addressed in February of 1999 when the February 11, 1999 New England Journal of Medicine published a landmark T3 Thyroid Drug Study that found that the majority of patients studied felt better on a combination of two drugs, including levothyroxine (T4) and T3, and NOT solely levothyroxine/T4 (i.e., Synthroid or Levoxyl) alone. The addition of T3 helped relieve depression, brain fog, fatigue and other symptoms.

Results May Aid Synthroid's Stepped-Up Sales Efforts

These study findings come shortly after an announcement by Knoll Pharmaceutical's parent company, BASF, indicating that they plan for their pharmaceutical activities to achieve a 15 to 20 percent return on sales in the upcoming year. Eggert Voscherau, a member f BASF's Board of Executive Directors with oversight for the company's Health & Nutrition segment, has said:

"We have set this return target as our priority, and we intend to achieve it by rapidly developing and marketing new drugs, consistently exploiting the potential of our drugs now on the market and increasing the focus of our activities."

Part of this effort is BASF Pharma's plans to implement targeted campaigns to fully take advantage of the market potential for some of its drugs, such as Synthroid.

How much more of the market Synthroid intends to capture, or how much more they plan to charge in order to increase their return, is a question that patients should seriously examine. Synthroid is already the number two drug sold in the U.S., has an estimated 85 percent of all the thyroid hormone market in the U.S.. After being embroiled in a class action lawsuit, a US district court approved settlement to give compensation to consumers who purchased the Synthroid between January 1, 1990 to October 29, 1999.

Archives of Internal Medicine 2000;160:526-534


Dr. Mercola's Comments:

For the purposes of the study, normal TSH range was a TSH level between 0.3 and 5.1. This is where most traditional medical impressions are mistaken. I use a modification of this range which is explained in the article section. The fact that forty percent of patients, a number that translates to millions of Americans, are already taking thyroid hormone and being treated by a doctor but are still not in TSH range is of great concern.


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