[Parathyroid hormone -- its mechanisms of action and issues on clinical application].

PTH, recently approved for severe osteoporosis in US and Europe, acts as an anabolic agent for bone when given intermittently. However, when continuously given, PTH acts as a catabolic agent for bone, as seen in primary hyperparathyroidism. The mechanisms by which PTH acts in opposite directions are largely unknown. In this review, some of the possible mechanisms will be discussed.