Is it safe to take thyroid hormones for weight loss?
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.
Prevention Tips
Seek 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 clothing. 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 had a very high concentration of thyroid hormone (from Hartung et al., 2010).
Case 2. A 50-year-old woman who had part of her thyroid gland removed was taking extra thyroid hormone to lose weight. She went to an ER because she had chest pain. She had an abnormal heart rhythm and was admitted to the hospital. Laboratory tests showed that her thyroid hormone concentration was very high. Her heart stopped while she was in the hospital, and she died (from Bhasin et al., 1981).
Case 3. A 32-year-old woman took a dietary supplement for weight loss that contained thyroid hormone and felt jittery. After calling her poison center, she stopped taking the supplement, and her symptoms resolved.
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What are thyroid hormones?
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 might 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 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 levothyroxine (Synthroid). Thyroid hormones increase the body’s metabolism, which can cause weight loss.
Can thyroid hormones promote 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 sometimes found as illicit additives in over-the-counter weight-loss supplements.
Do thyroid hormones have to be prescribed?
Unlike tightly regulated prescription medications, over-the-counter weight-loss products can contain several different hormones 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.
What are the side effects of taking thyroid hormones?
The human body is very sensitive to changes in thyroid hormone concentrations. Taking too much of a thyroid hormone can result in hyperthyroidism. People with hyperthyroidism can have a rapid heart rate, anxiety, heat intolerance, and stomach discomfort. In severe cases, confusion, elevated body temperature, and abnormal heart rhythms are possible. If thyroid hormone is taken in excess for a prolonged period of time, heart failure and osteoporosis (weakening of bones) can occur. Thyroid storm is a rare but life-threatening condition that can occur. When this condition causes death, it is usually due to heart failure or multiple organ failure.
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.
What should you do if you have an adverse reaction to thyroid hormones?
If you suspect someone has taken thyroid hormones inappropriately or is having an adverse effect to a thyroid drug or weight-loss supplement, do not make the person vomit. Use the webPOISONCONTROL online tool to get immediate help, or call your poison center at 1-800-222-1222. Whether online or by phone, expert guidance is always free, confidential, and available 24 hours a day.
