Is it Safe to Take Thyroid Hormones for Weight Loss?

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The Bottom Line

Thyroid hormones can be found in prescription medications and in some over-the-counter weight loss supplements. Thyroid hormones should not be used for routine weight loss.

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The Full Story

Thyroid hormones are approved by the US Food and Drug Administration (FDA) to treat hypothyroidism, the condition that results when the thyroid gland does not secrete enough hormones. Hypothyroidism can occur due to problems with the endocrine system or following thyroid removal, which may be necessary to treat thyroid cancer. Symptoms of hypothyroidism include fatigue, weight gain, thin hair, and cold intolerance. Hypothyroidism is diagnosed by blood testing and often requires lifelong treatment with thyroid hormones that are taken by mouth daily.

Prescription thyroid hormones work by replacing the natural hormone that is not being made because the gland is either not working properly or has been removed. The most commonly prescribed thyroid hormone is called levothyroxine (Synthroid®), but there are others available. Thyroid hormones increase the body’s metabolism which may cause weight loss. 

Since thyroid hormones can increase the body’s metabolism and promote weight loss, there has been interest in using them as a diet aid. Some people use prescription thyroid medications for this reason, but thyroid hormones are also sometimes found as illicit additives in over-the-counter weight loss supplements. Unlike prescription medications which are tightly regulated, over-the-counter weight loss products may contain several different hormone preparations of variable potency. Since over-the-counter weight loss products are dietary supplements, they are not supposed to contain prescription medications such as thyroid hormones.

Excess thyroid hormone consumption can result in symptoms of hyperthyroidism, a condition in which there is too much thyroid hormone present in the human body. In the short term, individuals with hyperthyroidism can experience a rapid heart rate, anxiety, heat intolerance, and stomach discomfort. In more severe cases, confusion, elevated body temperature, and abnormal heart rhythms can occur. If thyroid hormone is taken in excess for prolonged periods of time, heart failure and osteoporosis (weakening of bones) can occur. 

The human body is very sensitive to changes in thyroid hormone levels, and adverse effects can occur after consumption of relatively small amounts of thyroid hormone. Because of this, people should not take prescription thyroid hormones unless they are under the care of a doctor for the treatment of hypothyroidism. People should not take over-the-counter weight loss supplements that contain thyroid hormones. If unwanted or unexpected symptoms occur after taking over-the-counter weight loss products, seek medical attention as soon as possible.

If you suspect someone has taken thyroid hormones inappropriately or is having an adverse effect to a medication or supplement, do not make the person vomit. Help is available online with webPOISONCONTROL, and by phone at 1-800-222-1222. Both options are free, confidential, and available 24 hours a day.

Maryann Amirshahi, PharmD, MD, MPH, PhD
Medical Toxicologist

Poisoned?

Call 1-800-222-1222 or

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Prevention Tips

  • Seek testing/medical care if you suspect you have symptoms of hyperthyroidism or hypothyroidism. 
  • Only take prescription thyroid supplements if you have a history of hypothyroidism and are under the care of a physician. 
  • Never take other people’s prescription medication. 
  • Do not take over-the-counter weight loss supplements that contain thyroid hormones. 

This Really Happened

Case #1: A 29-year-old man was found dead in his home. Despite it being cold outside the windows were open and he was wearing little covering. He had a bottle of prescription thyroid hormone nearby that he had been taking for weight loss. His autopsy showed evidence of a heart attack and his blood work showed very high levels of thyroid hormone. 

Case #2: A 50-year-old woman with a history of having part of her thyroid removed was taking extra thyroid hormone to lose weight. She went to the emergency room because she was chest pain and was found to have an abnormal heart rhythm. She was admitted to the hospital and her labs showed that her thyroid hormone levels were very high. Her heart stopped while she was in the hospital and she died. 

Case #3: A 32-year-old woman took a dietary supplement for weight loss that contained thyroid hormone and felt jittery. After calling the poison center, she stopped the supplement and her symptoms resolved. 


For More Information

5 Reasons You Should Never Take Thyroid Supplements (Consumer Reports)

Thyrotoxicosis After Consumption of Dietary Supplements Purchased Through the Internet — Staten Island, New York, 2015 (Centers for Disease Control and Prevent)


References

American Thyroid Association. “Thyroid support” supplements contain significant amounts of thyroid hormone.

Bhasin S, Wallace W, Lawrence JB, Lesch M. Sudden death associated with thyroid hormone abuse. Am J Med 1981. 71:887– 890.

Hartung B, Schott M, Daldrup T, Ritz-Timme S. Lethal thyroid storm after uncontrolled intake of liothyronine in order to lose weight. Int J Legal Med 2010; 124:637–640.

Kang GY, Parks JR, Fileta B, et al. Thyroxine and triiodothyronine content in commercially available thyroid health supplements. Thyroid 2013;23:1233–1237.

Kaplan R. Thyroxine abuse. Aust N Z J Psychiatry 1998; 32:464–465.

Poon WT, Ng SW, Lai CK, Chan YW, Mak WL. Factitious thyrotoxicosis and herbal dietary supplement for weight reduction. Clin Toxicol (Phila). 2008 Apr;46:290-2.

Yen M, Burns-Ewald M. Toxicity of weight loss agents. Journal of Medical Toxicology 2012;8:145-152.

Poisoned?

Call 1-800-222-1222 or

HELP ME online

Prevention Tips

  • Seek testing/medical care if you suspect you have symptoms of hyperthyroidism or hypothyroidism. 
  • Only take prescription thyroid supplements if you have a history of hypothyroidism and are under the care of a physician. 
  • Never take other people’s prescription medication. 
  • Do not take over-the-counter weight loss supplements that contain thyroid hormones. 

This Really Happened

Case #1: A 29-year-old man was found dead in his home. Despite it being cold outside the windows were open and he was wearing little covering. He had a bottle of prescription thyroid hormone nearby that he had been taking for weight loss. His autopsy showed evidence of a heart attack and his blood work showed very high levels of thyroid hormone. 

Case #2: A 50-year-old woman with a history of having part of her thyroid removed was taking extra thyroid hormone to lose weight. She went to the emergency room because she was chest pain and was found to have an abnormal heart rhythm. She was admitted to the hospital and her labs showed that her thyroid hormone levels were very high. Her heart stopped while she was in the hospital and she died. 

Case #3: A 32-year-old woman took a dietary supplement for weight loss that contained thyroid hormone and felt jittery. After calling the poison center, she stopped the supplement and her symptoms resolved.