Osteoporosis is defined as a systemic skeletal disease characterized by low bone mass and microarchitectural deterioration of bone tissue, with a consequent increase in bone fragility and susceptibility to fracture risk. Osteoporosis affects one in three women and one in eight men during their lives. Most subjects who suffer from the disease are in the last third of their lives. Obviously, osteoporosis is widespread, and as the world’s population ages, more and more people will suffer from this debilitating and sometimes fatal disease.
Calcium (Ca) is an essential element of all cells and organisms. It is involved in many cellular functions, e.g. in cell signalling, enzyme secretion, cell aggregation, cell division and muscular contraction . Late in phylogeny, Ca became a major element of the skeleton only in higher vertebrates. Functionally replacing cartilage, bone has a higher compression and tensile strength . To carry the same weight, the cross-sectional area of cartilage must be 5 times greater than that of bone; therefore, the cross-sectional articular cartilage area is much larger than the adjacent cortical bone area.
Calcium is a major component of the skeleton. This often leads to the misconception that the major function of calcium for human health is its importance for a healthy, strong skeleton. Although the importance of having adequate amounts of calcium in the skeleton cannot be underestimated, it should be appreciated that calcium plays critically important roles in other metabolic, cellular and organ functions. Calcium is essential in chemical signaling within cells, promoting transmission of nerve impulses, inducing muscle contraction, initiating blood clotting, participating as a cofactor for many enzymes and hormones and regulating cellular proliferation and maturation.
Bone is a vital connective tissue that allows for structural support, locomotion and serves as a critical reserve for mineral homeostasis. The inorganic phase of bone, which makes up approximately 70% of its weight, is primarily a calcium phosphate mineral analogous to crystalline hydroxyapatite. Approximately 98% of the organic phase of bone is type I collagen. Noncollagenous proteins in bone include osteocalcin, osteopontin, fibronectin and others. These organic bone components contribute to bone structure and biological function, and their measurement in serum can provide information on bone resorption and formation.
The skeleton is a remarkable, exact and intricate structure, responsible for supporting our muscular system. It enables us to stand up, bend, move, i.e. to interact with the world. Clearly maintaining bone health can enable a functioning skeletal system through the seventh or eight decade after birth. From birth to death, the skeleton undergoes physiologically dramatic changes.