Anabolic agents

Natural and synthetic hormone-like substances used to promote growth in farm animals. Most are derived from reproductive steroid hormones — oestrogens, progesterone and testosterone — while others, such as zeranol and the stilbene oestrogens, are nonsteroidal, whether natural or man-made. Widely used in many countries as ear implants, they improve weight gain and feed efficiency, cutting the cost of meat production. Because residues can persist in edible tissues, their use is strictly regulated: maximum residue limits apply, some regions ban them outright, and international trade disputes have centred on differing national rules for hormone-treated meat.