The hallmark of this disease is brittle bones. The weak bones are due to a decreased absorption of calcium into the body and depletion of calcium and bone protein. It is a common type of metabolic bone disease in which bones become thinner and weaker as a part of ageing. The bones are subject to fractures and heal slowly, occurring especially in women following menopause. If it is left untreated, the skeletal bones will become fragile and some of them will be likely to break or fracture, especially the hip and spinal bones.