OTC Thyroid Drugs Pose Health Risks

Ingredients in OTC thyroid supplements have few benefits and may cause dangerous side effects, experts say.

So-called “thyroid support” supplements that can be purchased over the counter carry serious health risks few patients know about, according new research from the Mayo Clinic.

The drugs promise to improve thyroid function, jumpstart weight loss, and reduce fatigue, but include ingredients that may also deliver a host of other side effects, including elevated heart rate, arrhythmia, nervousness, and diarrhea, said senior investigator Victor Bernet, MD, who presented the findings October 27, 2011, at the American Thyroid Association annual meeting.

At issue are 2 hormones—triiodothyronine (T3) and thyroxine (T4)—which are regulated by the FDA and intended for use only in prescription drugs indicated to treat thyroid deficiency, such as levothyroxine (Synthroid, Levothroid). Derived largely from chopped-up, dehydrated animal thyroids, these hormones were present in 9 of the 10 OTC supplements Dr. Bernet and colleagues tested.

Just 5 of the 10 products tested listed animal thyroid gland as an ingredient. Amounts of T3 and T4 in the hormone-containing pills varied widely, with some delivering a dose of up to twice the daily requirement for a healthy adult, the researchers noted. Both findings underscore the need for stricter regulation of OTC thyroid support supplements, according to Dr. Bernet.

“These hormones have effects throughout the body, which is why they are controlled,” he said in a news release.

The supplements are widely marketed as a remedy for symptoms associated with thyroid disorders—for example, unexplained weight gain or lack of energy. Because these symptoms are so commonplace, patients may think it’s safer to choose an OTC supplement rather than consult with a physician to investigate their cause and explore therapy options.

But taking the pills without a physician’s guidance is not only dangerous, it’s unlikely to yield the desired effect, said Dr. Bernet, who also serves as chairman of the American Thyroid Association’s public health committee. He began studying thyroid support supplements after physicians reported cases of abnormal thyroid test results in patients who took them.

In addition to the need for better regulatory oversight, Dr. Bernet said there is a need to educate patients about the drugs’ risks—which likely outweigh any potential benefits from taking them.

"The amount of thyroid hormone a normal person would have to take to lose weight would be dangerously high and there is no evidence that use of thyroid hormone effectively treats fatigue when used in people without actual hypothyroidism," he said.

For other articles in this issue, see:

• Doctors Underestimate Language Gaps
• Weighing Obesity’s Impact on Flu Shots