骨格形成と環境

Abstract

The bone tissue of the fetus first appears after the 7th embryonic week. Cartilaginous structures are first formed and then replaced by bone. In the center of the cartilaginous precursor, calcified cartilage are deposited in the matrix and destroyed by invasion of vascular tissue with osteoblast and new bone. After birth, bone mineral metabolism and calcium homeostasis is regulated by parathyroid hormone with a complex interaction of its effects on bone remodeling, the renal excretion of calcium and phosphate, and via vitamin D-activated intestinal calcium absorptive mechanisms. Calcitonin is the antagonist to the osteolytic function of parathyroid hormone. The peak bone mass is achieved in the late teens or early twenties. Then, bone mineral density decreased continuously resulting in reduced bone strength and predisposition to fracture. Recently, osteoporosis has received much attention and has become an serious public health problem because it leads to fracture after minimal trauma. The pathogenesis and treatment of osteoporosis are reviewed and the environmental factors are discussed.