Weight loss & thyroxine

Updated February 21, 2017

Your thyroid gland can help or hurt your efforts to lose weight. If your thyroid gland is sluggish (hypothyroidism), you will begin gaining weight, but if you have hyperthyroidism or an overactive thyroid gland, you are going to be losing weight. So one way people have tried to lose weight is by stimulating their thyroid gland into being more active than usual.

Thyroid Gland

The thyroid gland's role in your body is to help it make the energy it needs, regulating the body's temperature and assisting other organs in their functions. In helping the body make energy, the thyroid manufactures two hormones, thyroxine and triiodothyrodine, that help burn fats, carbohydrates and protein to make the energy.


L-Thyroxine is a synthetic thyroid hormone. It mimics the function of one of the two naturally produced hormones of the thyroid gland, thyroxine. In high doses, both thyroxine and L-thyroxine accelerate the burning of fat even if you are consuming more calories than usual. In lower doses, the hormones will burn fat but they will also burn protein and carbohydrates. This can result in a loss of muscle mass.

What Happens

Thyroxine raises your metabolic rate. You will have more energy, burn more calories and lose weight. When you exercise, the levels of thyroxine in your blood will increase by 30 per cent or so and remain elevated. This will magnify the effects of the L-thyroxine.


Athletes will usually take L-thyroxine in a dose of 200-400 mcg/day to get the best fat-burning benefit without losing muscle. A large dose would be considered 400-600 mcg/day. You should start with low daily dose and gradually increase it over a week or so until you reach the 200-400 mcg range.

Side Effects

When used properly, L-thyroxine is usually safe. It will put your thyroid gland into overdrive and burn fat. However, high doses or doses that are increased too quickly can cause finger trembling, perspiration, diarrhoea, insomnia, nausea and elevated heart rate.

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About the Author

James Rada, Jr. was a newspaper reporter for eight years and earned 23 awards from the Maryland Delaware D.C. Press Association, Associated Press, Society of Professional Journalists, Maryland State Teachers’ Association and CNHI. He also worked for 12 years as a marketing communications writer, earning a Print Copywriter of the Year Award from the Utah Ad Federation. He holds a Bachelor of Arts in communications.