Are you referring to actual
T3 (as in thyroid hormone) or the guggul product
T3? If the former, I've used it fairly extensively; I usually include a low dose when eating maintenance calories to give myself a little padding, and go up to usually 100mcg/day when cutting. On cycle, I usually include 25mcg/day for the added
protein synthesis benefits (can't really tell a big difference either way, but it can't hurt).
With that said, definitely do some research before giving it a shot. Prolonged use can be catabolic to bone as well as muscle. If you haven't already, go over to CEM (Cutting Edge Muscle) and search for some of Nandi12's posts concerning it, or look through some of the older Mind and Muscle mags (mindandmuscle.net) for his article.
"I don't like people who take drugs...Customs men, for example." - Mitch Miller