T4 Hormone & Weightlifting

Body builders often turn to supplements to lose fat, build lean muscle mass and reduce recovery time after intense workouts. Because anabolic steroids are frequently banned in competitions, weightlifters turn to more natural supplements to produce results. The thyroid hormone T4 helps control the rate of metabolism, which is one reason athletes sometimes choose T4 to help give them a competitive edge.

A woman is doing a lateral pull down. Credit: bondarchik/iStock/Getty Images


T4 is also known as L-Thyroxine T4 and is available in several prescription formulations. It's one of two primary hormones your thyroid produces, the other being triiodothyronine, or T3, although T4 makes up 90 percent of thyroid hormone. Every cell in your body depends upon thyroid hormones to regulate their metabolic function. If the thyroid gland does not produce sufficient T4, then you may develop symptoms of hypothyroidism; too much T4 leads to hyperthyroidism, according to the American Thyroid Association.

The Effects of Weightlifting on T4

Research in Finland on elite weightlifters over a period of a year studied the response of the pituitary-thyroid system before, during and after strength training. The results, published in the "Journal of Sports Science" in 1993, showed that periods of decreased training leads to a mild decrease in serum T4 concentrations. Another study, published in 1995 in the "European Journal of Applied Physiology and Occupational Physiology," found that T4 levels in weightlifters were lower at night than in a control group, which the researchers concluded may have implications for muscle building. It's also been shown that male bodybuilders taking androgenic-anabolic steroids developed mild thyroid impairment.

Why Bodybuilders Use T4

Thyroid medication is frequently used by bodybuilders getting ready for a competition to lose excess fat by speeding up their basal metabolic rate and help them get "cut," or produce maximum muscle definition. Although the thyroid hormone T3 is more popular for this purpose, T4 may lead to increased muscle retention and improve the effects of growth hormone in weightlifters who are also taking growth hormone. Having excess thyroid hormones in your body can help produce more short-term weight loss than by dieting alone, but once the thyroid supplements are stopped, the excess weight loss is usually regained, reports the American Thyroid Association.


If you decide to add T4 to your weightlifting supplements, check with a health care provider first. Excess thyroid hormones can cause the symptoms of hyperthyroidism, including tremors in the hands, heart palpitations, diarrhea, nausea, very high perspiration, headaches and a goiter, or swelling in the neck. For maximum effectiveness, T4 shouldn't be taken within two hours of calcium or iron, which can reduce its absorption. Long-term use of thyroid hormones can suppress your body's natural production. When you stop taking it, it could take some time for levels to return to normal levels, and, according to MesoRX, in some cases your body may lose its ability to produce the hormones permanently.

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