Bone Structure and Metabolism

Abstract

Bones constitute a part of the musculoskeletal system that defines the shape of the body and protects vital organs. Bones are essential in movement, acting as a rigid lever for the action of muscles. In addition, they have a hematopoietic function and act as phosphorus and calcium (P/Ca) homeostasis regulators. Bone mass contributes to the maintenance of adequate levels of blood calcium. Mechanical integrity depends on a balance in the regulation of bone resorption and formation (coupling). The regulation of bone metabolism is mainly driven by three hormones: vitamin D, PTH, and calcitonin. Other hormones (thyroid hormones, estrogens, and hypothalamic control) exert a secondary influence.

The etiology of metabolic diseases is varied, but local or general remodeling is always present. The metabolic alteration could result in quantitative disease, with a reduction (osteoporosis) or an increase (osteosclerosis) of bone density, or produce qualitative bone alterations (osteomalacia).