As well as the joy of a new baby, women with MS often find pregnancy brings a second, unexpected gift - a break from relapses.
This effect has been revealed by studies that followed women with MS through pregnancy and childbirth. These studies show that women with MS are less likely to have relapses while pregnant, similar to the effects of current disease modifying therapies (DMTs). So what’s going on and what have hormones got to do with it?
Hormones are key
A major change during pregnancy is increased levels of certain hormones, such as oestrogen and progesterone. Hormones are chemical messengers. They deliver instructions to different parts of the body to ensure everything is working properly. Levels of oestrogen and progesterone in the body rise throughout pregnancy to prepare the body for changes that occur during pregnancy and labour.
Surprisingly, oestrogen and progesterone can also affect the immune system. They decrease immune activation, which prevents the body from viewing the baby as an intruder and provides a safe environment for development. A fortunate side effect of this more tolerant environment is a decrease in MS-related activity, because MS is an autoimmune condition. This leads to a reduced number of relapses.
What’s more, progesterone has been found to be neuroprotective in animal models of disease. It seems to not only prevent myelin damage, but promotes myelin repair.
Effects beyond pregnancy
These effects unfortunately only last as long as the pregnancy, with levels of oestrogen and progesterone returning to pre-pregnancy levels after birth. This can mean an increased risk of relapses in the first three months after childbirth, although this has been shown to have no long-term effect on disease progression.
How can we use the effects of increased hormone levels to combat MS? There has been a lot of excitement around using pregnancy hormones as therapies, and clinical trials looking at their effectiveness in women with MS have begun.
An initial study looked at the effectiveness of oral oestriol (a form of oestrogen made during pregnancy) in reducing relapses. This small trial suggested oestrial was effective at reducing MRI activity in relapsing remitting MS, but did not work for women with progressive MS.
A larger phase-2 study then looked at the effect of oestriol in combination with a DMT in women with relapsing remitting MS. The study showed the combination of oestriol and a DMT reduced the number of relapses by 47% compared to a DMT alone in the first year of treatment, although the effect was less obvious in year two of the trial.
These studies have highlighted the potential use of hormone therapy for women with relapsing remitting MS. Male-specific hormones are also being investigated as potential therapies for men with MS.
Larger phase-3 trials will be needed to definitively test their effectiveness. Whilst these results are encouraging, more research is needed to understand how pregnancy is affecting disease course in MS, and how we can use this to design more effective therapies in the future.
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