WASHINGTON (Reuters) - Scientists intrigued by the fact that multiple sclerosis can slip into remission when women are pregnant said on Tuesday a pregnancy-related hormone may offer great promise for treating the neurological disease. Researchers at the University of Calgary said a study involving mice showed that a hormone called prolactin triggers production of myelin, a fatty substance that insulates nerve cells in the brain and spinal cord. In multiple sclerosis, the immune system, which normally protects the body, is believed to attack the myelin that coats nerve cells, causing a worsening loss of sensation and movement that can range...