Over-the-Counter Thyroid Supplements

The Surprising Ingredient in Some Non-Prescription Metabolism Boosters

A selection of vitamins and herbal supplements
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Have you ever reached for an over-the-counter dietary supplement that claims to rev up your metabolism by providing "thyroid support?" While these products contain a mix of natural ingredients such as vitamins, minerals, and herbs, some may include ingredients that should be taken only under the direction of a doctor. So before you swallow a thyroid booster, here's what you should know about these popular supplements.

The Thyroid-Metabolism Link

The thyroid produces the hormones that control metabolism, the rate at which the body produces energy from nutrients and oxygen, according to the American Thyroid Association. If this gland doesn't pump out enough these hormones, metabolism slows down—a condition known as hypothyroidism.

The National Institutes of Health reports that just under five percent of people age 12 and over, mostly women, have a sluggish thyroid gland. Some with the condition don't even realize it, but others experience symptoms such as being tired and run down for no clear reason; unexplained weight gain; irritability; and feeling cold all the time.

To relieve these symptoms, a doctor, usually an endocrinologist, will have a person with hypothyroidism take medications contain thyroid hormones in prescription level doses. Someone who's on one of these drugs is especially vulnerable to problems if he also chooses to take an over-the-counter supplement.

The Problem With Supplements

Most contain a mix of vitamins, minerals, and herbs, but that may not be all. According to research published in 2013 in the journal Thyroid, many also may contain thyroid hormones typically found in thyroid hormone replacement drugs that are given by prescription to treat hypothyroidism.

For the study, scientists analyzed the ingredients in 10 popular OTC thyroid supplements. They found that nine out of the 10 products evaluated had detectable amounts of triiodothyronine (T3) ranging from 1.3 micrograms (mcg) to as much as 25.4 mcg per tablet. And five of the supplements, if taken at the recommended dosage, would provide more than 10 mcg of T3 per day. In addition, four of the products would deliver thyroxine (T4) in quantities ranging from 8.57 mcg per day to 91.6 mcg per day.

These are considered clinically significant amounts of T3 and T4. In fact, in some cases, the doses exceed amounts typically prescribed to treat hypothyroidism. The problem with this, according to the researchers, is that it puts people who take certain over-the-counter supplements along with prescription thyroid replacement medications at risk of hyperthyroidism, a condition in which the thyroid gland produces too much hormone.

Hyperthyroidism and Your Health

Hyperthyroidism, while less common than hypothyroidism, can lead to potentially serious complications. Some of the many health issues associated with hyperthyroidism are heart problems including rapid heart rate, an irregular heart rate (atrial fibrillation), and even congestive heart failure. The condition also can cause bulging, red, or swollen eyes, sensitivity to light, and blurred or double vision; redness and swelling of the skin on the feet and shins; and osteoporosis, because too much thyroid hormone interferes with the body's ability to incorporate calcium into the bones.

Another risk associated with hyperthyroidism is a sudden and serious intensification of symptoms called thyrotoxic crisis. This can lead to fever, a rapid pulse, and even delirium, and should be treated immediately.​

The bottom line, then, is to check with your doctor before taking any over-the-counter thyroid support supplement—especially if you're already on a thyroid hormone replacement medication. Otherwise, you could become overmedicated, putting your health at risk unnecessarily.



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Article Sources
  • Kang, G.Y. "Thyroxine and Triiodothyronine Content in Commercially Available Thyroid Health Supplements." Abstracts of the American Thyroid Association Annual Meeting, 2011.
  • Mayo Clinic. "Hyperthyroidism (Overactive Thyroid): Complications." Oct 28, 2015.
  • National Institutes of Health. "The Thyroid and You: Coping With a Common Condition." Medline Plus.