Prolactin, a hormone that the body naturally produces during pregnancy, may be a key to unraveling the mystery of multiple sclerosis, and could eventually lead to new treatments for the disease.

MS is a chronic disease characterized by the body's immune system turning against itself by destroying the myelin sheath, a fatty substance that coats neurons and makes it easier for them to transmit electrical signals. Loss of the myelin sheath gradually reduces a person's sensory and motor capabilities.

Many MS patients experience remission, or temporary cessation of symptoms, for reasons that are not fully understood. However, pregnancy is one condition that has been associated not only with remission, but also with repair of the myelin sheath in some cases.

In the latest study, the halting of myelin destruction, as well as the spontaneous production of myelin, was linked to the pregnancy hormone prolactin in pregnant mice. The findings are published in the Journal of Neuroscience.

Additional experiments with animals will be necessary, the researchers said, but they hope to progress to human trials involving the effect of prolactin on MS within the next few years.

Current treatments for MS can sometimes slow the progress of the disease, but so far there are no treatments that can reverse the damage it causes to the brain and spinal cord.

"This discovery has the potential to take MS therapy a step further than current treatments that stabilize the disease in its early stages," said Dr. Luanne Metz, director of the Calgary MS Clinic in the Department of Clinical Neurosciences. "By promoting repair, which is the goal of prolactin therapy, we have hope of actually improving symptoms in people with MS."