Thyroid Hormone Common Contaminant in Weight-Loss Supplements

Nancy A Melville

October 26, 2015

ORLANDO, Florida — Over-the-counter (OTC) weight-loss supplements commonly contain unlabeled and clinically significant levels of thyroid hormones, including thyroxine (T4) and triiodothyronine (T3), posing potentially serious health risks to users unaware of the contents, according to new research.

"One of the products that we tested had a higher dose of thyroid hormone than what someone would commonly be prescribed after having just had their thyroid gland removed, so this is not a trivial dose," first author Christian Seger, MS, of the David Geffen School of Medicine at the University of California, Los Angeles (UCLA), told Medscape Medical News.

"This should serve as an alert to consumers, because even if you were the most informed and educated of shoppers and understood thyroid physiology, you still would really have no indication of what you are getting in the product," Mr Seger said.

For the study, presented here at the 2015 International Thyroid Congress and Annual Meeting of the American Thyroid Association (ITC/ATA), Mr Seger and his colleagues evaluated 29 OTC weight-loss supplements available in the United States, selected for their popularity in stores and with online retailers, and had samples of the supplements measured for T4 and T3 content with high-performance liquid chromatography.

They found that a daily dose of one supplement marketed as a "thermogenic weight-loss agent" had as much as a mean 66.6 µg/day of T3 content.

"A T3 content of 66.6 µg per daily weight-loss-pill ingestion represents more than the T3 dose normally prescribed in the setting of thyroid cancer to achieve suppression of serum thyrotropin," senior author Angela Leung, MD, also of UCLA, told Medscape Medical News.

"As such, the T3 content of 66.6 µg is already more than the physiologic replacement dose in most individuals."

Another supplement, marketed as a "hard-core thermogenic," had a T3 content of 19.2 and T4 content of 29.6 µg/day, and a product sold as a "fat burner" had a T3 content of 27.1 and T4 content of 20.7 µg/day.

Of the hormone-containing supplements Mr Seger and his colleagues examined, those marketed as "hard-core thermogenics" had an average T3 content of 19.2 µg/day (n=2) and T4 content of 29.6 µg/day (n=1). Others, marketed as "fat burners," had average T3 content of 27.1 µg/day (n=3) and T4 content of 20.7 µg/day (n=2).

Three other products also had measurable levels of T3 and/or T4.

Numerous Potential Adverse Effects

The potential adverse effects of unknowingly ingesting relatively high levels of thyroid hormone and thereby increasing metabolism are numerous, Dr Leung said.

"Effects may include signs and symptoms of thyrotoxicosis, such as weight loss, palpitations, heat intolerance, menstrual irregularities, and if they are used over a prolonged period of time or in high doses acutely, atrial fibrillation and bone loss," she explained.

Those with underlying thyroid disease could be particularly at risk for thyrotoxicosis stemming from thyroid-hormone excess, and the risk could even extend to those without underlying disease, she noted.

"The average consumer should not be expecting to find any thyroid-hormone content in over-the-counter weight-loss products," Dr Leung stressed.

"Thyroid hormones are prescription-only medications that should be used only in the setting of conditions requiring thyroid-hormone replacement, such as hypothyroidism and thyroid cancer management."

The findings come on the heels of a study published just a week before the meeting (N Engl J Med.2015;373:1531-1540), as reported by Medscape Medical News, detailing that more than 23,000 emergency-department visits per week and an estimated 2154 hospitalizations annually in the United States can be attributed to adverse events related to dietary supplements.

Among those visits, about 25% of cases were attributed to herbal or complementary nutritional products for weight loss.

"Weight-loss or energy products caused 71.8% of supplement-related adverse events involving palpitations, chest pain, or tachycardia, and 58.0% involved persons 20 to 34 years of age," wrote the authors, led by Andrew I Geller, MD, of the Centers for Disease Control and Prevention's Division of Healthcare Quality Promotion, in Atlanta, Georgia.

While those symptoms could be attributable to the slew of ingredients that have been shown to make their way into weight-loss supplements, such as ephedra (banned by the US Food and Drug Administration) and caffeine, they also fit the bill for thyroid overtreatment, which is not as commonly suspected and therefore possibly even more of a risk.

Not Much Awareness of Risk of Contamination With Thyroid Hormones

"It's a surprise to see these levels of thyroid hormone in these supplements, and I don't think there is much awareness of this risk," Lewis E Braverman, MD, also a coauthor on the study presented at ITC and professor of medicine at Boston University Medical Center, Massachusetts, told Medscape Medical News.

The study isn't the first to show troubling levels of thyroid hormone in OTC supplements, however. In research published in 2013 (Thyroid. 2013;23:1233-1237), a review of 10 commercially available thyroid dietary supplements marketed for "thyroid support" showed that nearly all — nine of the 10 — had detectable levels of T3 (1.3–25.4 μg/tablet) and five of the 10 samples contained T4 (5.77–22.9 μg/tablet).

If taken at their recommended doses, five of the supplements contained T3 quantities that were greater than 10 μg/day, and four had T4 quantities ranging from 8.57 to 91.6 μg/day.

"These amounts of thyroid hormone, found in easily accessible dietary supplements, potentially expose patients to the risk of alterations in thyroid levels even to the point of developing iatrogenic thyrotoxicosis," wrote the authors, led by Grace Y Kang, MD, of the department of endocrinology, division of medicine at Landstuhl Regional Medical Center, Germany.

"[The findings] emphasize the importance of patient and provider education regarding the use of dietary supplements and highlight the need for greater regulation of these products, which hold potential danger to public health."

The authors had no relevant financial relationships.

2015 International Thyroid Congress and Annual Meeting of the American Thyroid Association; Orlando, Florida. Short Call Poster 54, presented October 22, 2015.

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