Pediatricians say the onset of menstruation has steadily decreased in recent decades.
Early onset of puberty with its raging hormones translates into higher risk of breast cancer, said Sonnenschein. Unless you are exposed to estrogens you don't get breast cancer. The longer the exposure is, the higher the incidence. Hormones are used by cattle farmers in Canada and the United States to increase the weight of cattle prior to slaughter. They are currently the focus of a major trade dispute between North American and the European Union.