Morphological analysis of bone dynamics and metabolic bone disease. Effects of parathyroid hormone on bone tissue

: Parathyroid hormone (PTH) is a major hormonal regulator of calcium homeostasis. Continuous exposure of bone to PTH results in a net catabolic or resorptive response, whereas intermittent exposure to PTH leads to dramatic increases in bone formation and bone volume. Anabolic effects of PTH on bone have been demonstrated histologically in osteopenic animal models and in human osteoporosis. PTH increases the size of remodeling space and the number of basic multicellular units, resulting in a positive bone balance. PTH treatment also induces modeling bone formation at quiescent surfaces. PTH can increase and re-establish trabecular connectivity with a shift toward a more plate-like structure.