It may shock many people to know that T3 is NOT catabolic per se. Corticosteroids are catabolic drugs that attack muscle tissue directly; T3 does not. It is a very potent calorie burner and it does not discriminate between carbohydrates, protein and fat. Unlike DNP, it has no protein sparing properties. T3 is also more likely to burn muscle than fat in lean users (10-12% BF), but this can be said for any extreme drop in caloric intake and uptake such as starvation diets (Caloric intake <10 X BW).
Muscle loss can be avoided with the use of anabolic agents. T3s alleged catabolic properties have become legendary. Excessive amounts of T3 (more than 75mcg), will have a very strong calorie burning effect, and since some bodybuilder use 150 mcg, its easy to see why such misinformation has been so prevalent. The average bodybuilder will not need several grams of steroids to counter a reasonable dose of T3. There is no need to use more than 75mcg-100mcg. Going beyond this dose will cause more harm than good, as massive doses of steroids need to be used to counter the muscle loss, further stressing the body for minimal, if any additional benefits.