Chapter 9 - Immunoassays for PTH and PTHrP: Clinical Applications

Abstract

This chapter focuses on the development and clinical application of immunoassays for circulating levels of Parathyroid Hormone (PTH) and Parathyroid Hormone-Related Protein (PTHrP). The accurate and precise measurement of circulating levels of PTH has revolutionized the clinical management of patients with calcium and skeletal disorders, and assays for PTHrP have comparable clinical impact for the patient with hypercalcemia, especially hypercalcemia due to cancer. This chapter also reviews the expanding information on the application of PTHrP immunoassays to clinical diagnosis and management. In contrast to PTH, assays for PTHrP are in their early stages of development are complicated by the more complex biosynthesis, secretion, and metabolism of this polypeptide. Sensitive and specific assays for PTH and PTHrP aid in the differential diagnosis of hypercalcemia, hypocalcemia, and a variety of other calcium and skeletal diseases. In addition to their usefulness in clinical management, PTH and PTHrP serum assays help in elucidating the pathophysiology of many disorders of calcium and skeletal metabolism. Serum PTH immunoassays are invaluable in the differential diagnosis of hypercalcemia and hypocalcemia. In general, all well-characterized PTH immunoassays can serve this function, even though studies have focused on assays of the intact PTH. With many assays available, a practical approach to the differential diagnosis of calcium disorders is to use the PTH immunoassay —that is, readily available and interpretable to the physician.