Prohormones are in a simple way to put it precursors or derivatives of steroidal hormones. While they often carry with them strong similarities they in many cases cannot be labeled anabolic steroids. However, in recent years many prohormones have been found to be so closely related to schedule III steroids they have been banned under the banner of illegal steroids by way of the Steroid Control Act of 2004. The Steroid Control Act of 2004 was an addition to the original Steroid Control Act of 1990 placing many other hormone or hormonal related drugs on the banned list classified as illegal steroids. Many of these prohormones come out year after year and remain legal for a time but generally each one is eventually pulled off the shelf; but year after year anabolic science produces new models ready for legal use; at least for a time.