[The metabolic mode of circulating parathyroid hormone]

The circulating immunoreactive parathyroid hormone (PTH) exists in more than one form in plasma. These immunoreactive forms of PTH consists of intact hormone (large molecular weights) and lower molecular weight hormonal fragments from both the carboxyterminal and aminoterminal portions of PTH molecules. The most of the secreted intact PTH is cleaved or degraded in kidney and liver with forming C-terminal PTH. A little amounts of PTH are metabolized in bone or in other tissues bearing PTH/PTHrP receptor. This chapter reviews the mode of PTH metabolism in the peripheral tissues.