T3( Liothyronine Sodium) in the body is responsible for regulating the uptake of various nutrients into cells and into the mitochondria of those cells in order to effectively become utilized for the production and consumption of energy.
The bodybuilding and athletic world is attracted to the use of T3 as a physique and/or performance enhancing drug because of its capability to distinctly boost the body’s metabolism in the effort to metabolize body fat at a greater rate.
T3 is traditionally utilize during cutting, dieting, and/or pre-contest phases of training due to the universal goal of these phases to break down body fat, though in recent years T3 has gained some popularity as a useful agent during bulking and mass gaining phases of training (normally in conjunction with anabolic steroids) in order to better efficiently process nutrients and/or to keep body fat levels down during periods of higher caloric intake.
 

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T3 is commonly used with anabolic steroids due to its significant impact on the body's metabolism as a whole. It is very important to understand that T3 is indiscriminate in its metabolism boosting properties – it will increase the metabolism of fats, carbohydrates, and protein all equally.
Therefore, beyond a particular dose of T3, there is an increased risk of muscle loss through increased turnover of protein. Through the use of anabolic steroids and a properly adjusted diet, this muscle loss as a result of T3 can be prevented as a result of the nitrogen-retaining and protein sparing properties of theanabolic steroids.
T3 is also commonly combined with other fat loss agents in order to increase its overall effect, as it does work synergistically with other fat loss agents.