People with restless leg syndrome, or RLS, have a creepy-crawly feeling in their legs. This causes an irresistible urge to move the legs. It's a major cause of sleep loss, as the symptoms are most likely to occur at night. It has been found that brain cells need iron, oxygen carried by hemoglobin, and activation. They get nutrients from transport molecules that carry iron from the blood. Normal brain cells have doorways that let these transport molecules into the cell. Patients with restless leg syndrome lacked these portals, known as transferrin receptors. This means in spite of adequate amounts of iron in the blood not enough of it can enter the brain to prevent molecular damage.