[Aging bones as a paradigm for individual differences in aging]

The physiological fate of every organism and its organ systems is aging which--as general opinion has it--after the age of 50 leads to a measurable mass of bone loss in the human skeletal system. This so-called physiological osteoporosis, however, affects the individual bones differently: Thus, the volumetric density in the neck of the femur and in the lower three lumbar vertebral bodies (LVB) decreases by 30%, but not in the lower three cervical vertebral bodies (CVB), while in the thyroid cartilage it increases constantly from the age of 15/20 years onwards. From the functional point of view, the so-called osteoporosis of old age is thus an expression of an aging bone adapting to the physical activity of the body, which, as such--just like the bone of the younger adult--merely reflects the current stressing of the cancellous bone by the locomotor system. Osteoporosis proper, in contrast, is a manifestation of disease of the bone causing clinical symptoms, in which underlying osteopenia results in fractures and spontaneous deformations.