Signal transduction in the parathyroid.

PURPOSE OF REVIEW: To review recent developments regarding the mechanisms underlying the regulation of various aspects of parathyroid function.

RECENT FINDINGS: New studies published during the past year focused on calcium sensing via the calcium-sensing receptor, signal transduction within parathyroid cells, regulation of parathyroid hormone secretion, and the role of caveolae in calcium-sensing receptor-mediated signal transduction. In recent years, in-vitro and in-vivo studies have suggested a dominant role for the calcium-sensing receptor in the regulation of not only parathyroid hormone secretion but also parathyroid cellular proliferation by extracellular calcium. The development of a mouse model for primary hyperparathyroidism that over expresses cyclin D1 in the parathyroid gland provides an experimental system for studying the molecular basis for reduced calcium receptor expression and its role in the pathophysiology of primary hyperparathyroidism. There is also increasing evidence for the importance of vitamin D and the level of inorganic phosphate in regulating parathyroid function.

SUMMARY: Important advances are being made in understanding extracellular calcium- and calcium-sensing receptor-regulated signal transduction in the parathyroid but the subsequent steps coupling the calcium-sensing receptor to the control of parathyroid hormone secretion and parathyroid cellular proliferation remain to be fully elucidated.