[Osteoporosis. 1]

This article reviews the available data considering the question of pathogenesis and diagnostic of osteoporosis. Low bone mass can occur because there is insufficient bone deposited in the skeleton during growth, modelling, or because bone tissue is subsequently lost, remodelling. Peak bone mass is largely under genetic control, adequate nutrition during growth. Bone loss results from disturbance of bone remodelling, a continuous preventive maintenance programme in the adult skeleton. Bone remodelling is a quantum phenomenon that occurs in discrete units in four phases. Calciotropic hormones modulate the bone-cell production rate of cytokines and growth factors. Cytokines also locally mediate the effects of several hormones on bone cells. Disruption of the remodelling cycle at one of several points will lead to bone loss. Osteoporosis is a disease characterised by low bone mass per unit volume, microarchitectural deterioration of bone tissue leading to enhance bone fragility, and a consequent increase in fracture risk.