Steroids are a synthetic version of the human hormone testosterone that can stimulate muscle and bone growth but also cause negative side effects. For men, side effects include baldness, breast development, and testicular shrinkage. For women, side effects include facial hair growth, changes to their menstrual cycle, and breast reduction. Additional common side effects are liver damage, high blood pressure, and joint problems. Steroids were first developed in the 1930s and used by soldiers but were found to have more disadvantages than benefits for most medical purposes. Abuse of steroids in sports began in the 1950s Olympics, with some athletes developing such severe side effects that medical tests were needed to verify their gender.