[Effects of parathyroid hormone on bone metabolism : differences between intermittent and continuous treatment]

Numerous animal experiments and human studies have shown that intermittent injection of parathyroid hormone (PTH) exerts anabolic effects by increasing bone mass, whereas continuous PTH treatment decreases the bone mass. Thus, PTH has diverse effects on bone metabolism depending on the mode of administration. Several reports suggested that the duration of the serum concentration of PTH above the baseline level of endogenous PTH is a critical factor in regulating such anabolic and catabolic actions on the bone mass. However, the molecular mechanism of different PTH actions is not fully understood yet.