1. Inverse sigmoidal relationship between parathyroid hormone (PTH) release and the extracellular calcium concentration in human studies (upper panel) and in vitro in human parathyroid cells (bottom panel). Studies shown in the upper panel were performed by infusing calcium and the calcium chelator EDTA into normal subjects. Serum intact PTH was measured by a two-site immunoradiometric assay. In the lower panel, PTH was measured in the medium surrounding parathyroid cells in vitro by an assay for intact PTH. The midpoint between the maximal and minimal secretory rates is defined as the set point for secretion. (Redrawn, with permission, from Brown E. Extracellular Ca2+ sensing, regulation of parathyroid cell function, and role of Ca2+ and other ions as extracellular [first] messengers. Physiol Rev. 1991;71:371.)
Source: Disorders of the Parathyroids & Calcium & Phosphorus Metabolism, Pathophysiology of Disease: An Introduction to Clinical Medicine, 7e
Citation: Hammer GD, McPhee SJ. Pathophysiology of Disease: An Introduction to Clinical Medicine, 7e; 2013 Available at: Accessed: September 30, 2017
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