Three are natural hormones -- estradiol, progesterone and testosterone -- and three are synthetic hormones -- zeranol (an estrogen), trenbolone acetate (a steroid with androgen effects) and melengestrol acetate (a progestin), the study authors said.

• 三种是天然激素??雌二醇，孕酮和睾酮，三种是合成激素??折仑诺（一种雌激素），醋酸去甲雄三烯醇酮（一种有雄激素作用的类固醇）和醋酸美仑孕酮（一种黄体酮），研究人员说。