MECHANISM OF ACTION OF PARATHYROID-HORMONE

This paper reviews the processes involved in the transmission of information carried by parathyroid hormone (PTH) to the hormone responsive target. It discusses signal presentation at the cell surface, transduction across the membrane, transfer to the appropriate intracellular systems, and the integration of the cellular response. A model is presented to explain how the cell interprets the information presented by dynamic changes in PTH concentration. This model proposes that two G-protein coupled second messenger systems (adenylate cyclase and phospholipase C) act together to produce the range of cellular responses to PTH. It also suggests that the interpretation of the PTH signal by the cell depends upon differential activation of the two pathways.