The present invention discloses administering steroid hormones to mammals to treat autoimmune related diseases, more particularly, Th1-mediated (cell-mediated) autoimmune diseases including: multiple sclerosis (MS), rheumatoid arthritis (RA), autoimmune thyroiditis and uveitis. Most preferably the invention is used to treat a patient with a therapeutically effective amount of estriol of 8 milligrams once daily via oral administration to treat the symptoms or prevent the onset of multiple sclerosis.