Multiple Sclerosis Health Center

Primary Progressive MS and Gender

Most forms of multiple sclerosis strike women twice as often as men. Primary progressive MS, though, affects men and women in nearly equal numbers, baffling researchers. Let's explore the facts and what's understood at this point.

Men, Women, and Multiple Sclerosis

Multiple sclerosis may be an autoimmune disease, and autoimmune diseases generally affect women more than men. Overall, women make up about 75% of those living with autoimmune disease. For illnesses such as lupus and thyroid disease, women outnumber men by as much as 10 to one.

Multiple sclerosis follows a similar pattern. Among people who develop MS before the age of 20, women outnumber men by three to one. Looking at people of all ages, at least twice as many women as men are living with MS. But that's not all. The ratio of women to men with MS may be rising even higher. Some recent estimates place the number at four to one -- and suggest it is still going up.

Why the gender preference? This question has puzzled multiple sclerosis researchers for decades. Although intense study has yielded a few answers, it's raised even more questions. Then, when you consider primary progressive MS, the story gets even murkier.

Sex Hormones and Multiple Sclerosis

Multiple sclerosis doesn't target all women equally. Nearly always, MS attacks during the childbearing years. Symptoms often increase after childbirth or at the end of a menstrual cycle.  

When men develop multiple sclerosis, it's more often in their 30s or 40s -- just about the time their testosterone levels start to decline. Taken together, these clues suggest that sex hormones, like estrogen and testosterone, may be involved.

In one small study, 10 men with relapsing-remitting MS received testosterone gel for one year. There was no measurable difference in their MS as measured by imaging (MRI) of their brains. However, they had less brain "shrinkage" (atrophy) and were mentally sharper after receiving steroids.

In studies of women with MS, no high or low levels of any hormone seemed significant. However, the ratio of progesterone to estrogen went up during MS attacks.

Generally, studying hormone levels in men and women with MS has yielded interesting but confusing results. Sex hormones are likely involved in MS, but in complex ways that can't be summarized. It may be the balance of hormones, rather than their actual levels, that's most important.

The 'Equal Opportunity' MS

Overall, multiple sclerosis strikes three women for every man with the illness. But in primary progressive MS, this gender gap evaporates. Nearly equal numbers of men and women suffer this form of multiple sclerosis.

Primary progressive MS is marked by a steady march of symptoms from the time of diagnosis. There are no attacks with subsequent improvement, as in the more common forms of MS.