Interní Med. 2008; 10(5): 224-226

Dual action of parathormone and bone

prof. MUDr. Petr Broulík DrSc

III. interní klinika VFN a 1. LF UK, Praha

PTH is a hormone that increases the plasmatic level of calcium, maintains the level by mobilisation of calcium from bones with the help of osteoclastic resorption. Receptors for PTH and rP are situated on a cell membrane of osteoblasts, preosteoclasts. The bone involvement-bone changes caused by PTH over secretion are described as hyperparathyroid osteodystrophy. Unusual variability and nonconsistance of bone changes are unfortunately the main cause why such a high number of PHPT is recognized very late. PTH in a surplus is very aggressive towards bones, it dilutes bone mineral, stimulates osteoklasts and fibrous rebuilding of bones, leads to cyst formation and to formation of large brown tumours. Though hyperparathyroid osteodystrophy is a generalized disease, it does not involve the skeleton symmetrically, some regions remain practically intact; in other bones changes of all kind may be accumulated. In PHPT a bone turnover is increased, mainly in cortical bone, so the most specific and the most frequent X-ray finding is subperiostal resorption of radial and ulnar surface of distal hand phalanges. A small amount of PTH given in pulses behaves completely differerently. It activates preferentially osteoblasts, cells that form bones and only a little cells resorbing bones (osteoclasts). It increases the level of bone remodelation, increases new bone formation more than resorption.

Keywords: parathormon, osteoclastic resorption, hyperparathyroid osteodystrophy, anabolic activity of small doses of parathormon

Published: June 1, 2008  Show citation