Vitamin D deficiency: a culprit in metabolic bone disease.

Bone formation and bone remodeling are complicated processes regulated by systemic hormones and paracrine factors which regulate calcium and phosphate fluxes and cellular differentiation. The many actions of vitamin D reinforces its importance in the process of growth, maturation and aging of bone. An understanding of these important regulators of bone metabolism is important to understanding the clinical disorders as they are related to alterations in vitamin D metabolism and metabolic bone disease. Specific disorders of vitamin D metabolism can be related to clinical disease states of aging, altered lifestyles, gastrointestinal, renal and hepatic disease. A classification of altered vitamin D metabolism as related to its clinical states is presented. The scope of vitamin D deficiency from childhood rickets to adult osteomalacia and osteoporosis is presented, Intermediate syndromes of high turnover osteoporosis, subclinical vitamin D-deficiency states, role of vitamin D analogues in treating type I and type II osteoporosis is discussed. Treatment guidelines for managing this scope of clinical vitamin D disorders are provided.