Anabolic steroids increase the production of red blood cells, which increases the amount of circulating oxygen and promotes tissue growth. Testosterone, made by the testes, is a naturally-occurring anabolic steroid. Synthetic anabolic steroids are similar to testosterone, but they don’t have as many masculinizing effects. Anabolic steroids are used to treat chronic, non-regenerative anemia in pets. They also are used to increase muscle mass, improve body weight and condition in older dogs and restore weight and body condition in animals after surgery or debilitating disease.