Parathyroid Hormone Secretion and Serum Calcium Concentration - A Deterministic View of its Regulation

Abstract

In seven normal men we investigated the basal secretion of PTH by blood sampling in 30 sec intervals for estimation of intact PIH and at 2-min intervals for measurement of ionized calcium. In 4 of these subjects we also investigated the PTH-secretion under conditions of intermittent hypercalcemia and hypocalcemia. Our measurements demonstrate the existence of three time scales in the secretion of PTH, viz, short-term pulses (faster than 2 min), an intermediate pattern of adjusting PTH levels to changed Ca²⁺ averages, and finally a long-term coupling between PTH and Ca²⁺ averages after 20 min. Ionized calcium controls the long-term regulation and intermediate adaptation mechanisms, but the short-term fluctuations seem to be due to spontaneous secretion.

Parathyroid Hormone Secretion - Hypocalcemia - Hypercalcemia - Deterministic Aspects