How pregnancy eases multiple sclerosis

Women with multiple sclerosis tend to experience a temporary remission of the disease during pregnancy. Prolactin, a lactation-inducing hormone whose concentration increases during pregnancy, might be responsible for this effect, according to neurobiologist Samuel Weiss and colleagues at the University of Calgary (J. Neurosci. 2007, 27, 1812). Multiple sclerosis gradually destroys the myelin sheath that insulates and protects nerve fibers and enables them to conduct electrical signals effectively. As the disease progresses and myelin damage worsens, patients lose strength and dexterity, find walking increasingly difficult, and develop sensory problems. The Calgary researchers studied mice to determine the effect of prolactin on myelin. On the basis of their results, they propose that prolactin increases the number of myelin-forming cells and stimulates repair of damaged myelin in pregnant mice. The hormone has the same effects when given to virgin mice with myelin damage. If future animal trials bolster these results, Weiss says, prolactin could be tested as a treatment for humans.