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Dallas Scientists Discover Statins May Falsely Indicate Thyroid Problems
01/05/2009

DALLAS — Cholesterol-lowering statins, used daily by millions of Americans to treat and prevent atherosclerosis, may falsely indicate thyroid problems in some patients, according to researchers at Texas Health Presbyterian Hospital Dallas.

Their study, “Radioiodine studies, low serum TSH, and the influence of statin drugs,” appears in the journal Thyroid.

Dr. William Harvey, left, and Dr. Patrick Barr co-authored a study on radioiodine, low serum TSH, and the influence of statin drugs.

Dr. William Harvey, left, and Dr. Patrick Barr

Click image for hi-res file.

“These findings could help physicians make quicker, more accurate diagnoses of suspected thyroid problems,” said Dr. William Harvey, a nuclear medicine physician on the medical staff at Texas Health Presbyterian Dallas and an author of the study. “It also has very provocative scientific implications as we learn more about how statins affect different systems in the body.”

The researchers at Texas Health Presbyterian Dallas re-examined 307 patients whose initial TSH blood tests, the most common way to measure thyroid function, showed overactive thyroids. The condition, called hyperthyroidism, affects every part of the body, stimulating metabolism and affecting cellular activity throughout the body.

Symptoms of hyperthyroidism include a fast heart rate and palpitations, tremors, anxiety, weak muscles, and difficulty sleeping. If left untreated, hyperthyroidism can cause serious heart and bone problems.

For their study, the researchers at Texas Health Presbyterian Dallas administered more specialized diagnostics than the simple TSH blood tests, including radioiodine studies and other blood analyses. These new tests showed that the majority of patients on statins who appeared to be hyperthyroid by TSH tests actually had normal thyroid function.

The tests also confirmed that the majority of patients not taking statins did indeed have thyroid problems, as the initial TSH tests suggested.

Statins, considered one of the most important medical advances in the fight against heart disease, stroke and peripheral vascular disease, appear to either affect thyroid function or affect the results of common thyroid tests.

Dr. Mark Feldman is chairman of internal medicine at Texas Health Presbyterian Dallas.

Dr. Mark Feldman

Click image
for hi-res file.

These findings are fascinating because there’s a possibility that statins may improve thyroid function in patients with overactive thyroids,” said Dr. Mark Feldman, chairman of internal medicine at Texas Health Presbyterian Dallas and senior author of the study. “It could be an unexpected but delightful consequence of this research one day.”

Hyperthyroidism affects about 4 million people in the United States. Graves’ disease is the most common form of the condition, which occurs when the body’s immune system mistakenly attacks the thyroid gland and causes it to overproduce the hormone thyroxine.

The higher thyroxine levels caused by Graves’ disease can greatly increase the body’s metabolic rate, leading to host of health problems.

“This paper is important because it suggests that most people on statins for high cholesterol likely do not have any problem with their thyroid — even if they have low TSH test results (usually an indicator of an overactive thyroid),” said Dr. Patrick Barr, chief of nuclear medicine at Texas Health Presbyterian Dallas and co-author of the study. “That’s important because patients and their doctors might choose to not undergo a lot of expensive, invasive tests.”

Their paper also raises the question of whether something about statin drugs might one day be utilized to treat thyroid conditions. Statins, in addition to lowering the level of LDL cholesterol in the blood, have anti-inflammatory properties, which could affect other systems in the body, including the thyroid and other glands and organs, the researchers theorize.

“This may, theoretically, account for the connection between statin use and normal thyroid function, even with changes in TSH levels,” Feldman said. “It’s something that needs to be investigated further.”

The symptoms of hyperthyroidism are typically so gradual in their onset that patients don’t realize the symptoms until they become more severe. This means the symptoms may continue for weeks or months before patients fully realize they’re sick.

In older adults, some or all of the typical symptoms of hyperthyroidism may be absent, and the patient may just lose weight or become depressed.

“Further prospective studies of serum TSH and thyroid hormone levels before, during, and after stopping statin therapy would be of great interest,” Harvey said. “Right now, there is no therapeutic value in what we’ve found, but the hope is that this study is the beginning of more research into the topic.”

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About Texas Health Resources
Texas Health Resources is one of the largest faith-based, nonprofit health care delivery systems in the United States and the largest in North Texas in terms of patients served. Texas Health’s system of 13 hospitals includes Texas Health Harris Methodist, Texas Health Arlington Memorial, Texas Health Presbyterian, and a medical research organization. Texas Health is a corporate member or partner in six additional hospitals and surgery centers. For more information about Texas Health Resources, visit www.texashealth.org.

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