Female hormones – oestrogen and progesterone – affect much more than a woman’s reproductive system. It is thought they may also influence the immune and nervous systems, and, some scientists believe that they play a role in MS, though research has yet to show what this role might be. Women also have the hormone testosterone in their bodies. One small study reported that women with MS may have lower levels of testosterone than women without MS, but showed no significant difference in the levels of testosterone between men with and without MS. There have been no large scale studies in this area, and more research is needed to see if the endocrine system – the bodily system that produces hormones – is abnormal in people who have MS.