Monitor displays readings while patient lies in bone densitometer that measures the optical density of the patient's backbone by shining light on it and measuring its transmission to diagnose osteoporosis. Osteoporosis is caused by loss of the protein matrix in bones, and is a natural part of aging. The condition is especially severe in post-menopausal women due to loss of the hormone estrogen, which helps maintain bone mass. The bones become brittle, weak and liable to fracture.