T3 is not an anabolic/androgenic steroid but a thyroid hormone. As a substance it contains synthetically manufactured liothyronine sodium which resembles the natural thyroid hormone tricodide-thyronine (L-T3). The thyroid of a healthy person usually produces two hormones, the better known L-thyroxine (L-T4) and the aforementioned L-triiodine-thyronine (L-T3). Since T3  is the synthetic equivalent of the latter hormone, it causes the same processes in the body as if the thyroid were to produce more of the hormone. It is interesting to note that L-T3 is clearly the stronger and more effective of these two hormones.