Vitamin D and its metabolites in the pathogenesis and treatment of osteoporosis

Vitamin D and calcium are essential for normal skeletal growth and for maintaining the mechanical and structural integrity of the skeleton. Reduced intake of calcium and vitamin D may be associated with reduced bone mass and osteoporosis while a chronic and severe vitamin D deficiency may lead to osteomalacia. 1,25(OH)2D (calcitriol) is the major active metabolite of vitamin D and promotes intestinal calcium absorption and the mineralization of bone matrix and reduces PTH secretion. Despite vitamin D and calcium are considered essential components of management strategies for the prevention and treatment of osteoporosis, many people do not have adequate vitamin D levels. Vitamin D insufficiency is particularly common in the elderly due to reduced exposition to sunlight, declined synthesis of vitamin D in the skin and impaired renal hydroxylation. Even though secure inferences from randomized controlled trials on the prevention of osteoporotic fracture with vitamin D or its metabolites are limited, these compounds have been demonstrated to be pharmacologically active, safe and cost-effective for the prevention of age-related bone loss. Their use should be encouraged expecially in elderly subjects or in condition of dietary deficiencies. Interestingly, health benefits of vitamin D and its analogues may go beyond osteoporosis, including prevention of cancer and autoimmune diseases and improvement of neuromuscular function.