Parathyroid Disorders

Morri E. Markowitz; Lisa Underland; Robert Gensure

doi:10.1542/pir.2015-0076

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Morri E. Markowitz, MD*
Lisa Underland, MD*
Robert Gensure, MD*

^*Department of Pediatrics, Albert Einstein College of Medicine, Bronx, NY.

AUTHOR DISCLOSURE
Drs Markowitz, Underland, and Gensure have disclosed no financial relationships relevant to this article. This commentary does not contain discussion of an unapproved/investigative use of a commercial product/device.

Practice Gap

Hypocalcemia is not uncommon in pediatric practice, but hypercalcemia is. Clinicians should improve their ability to recognize the variants in the differential diagnosis related to parathyroid diseases.

Objectives

After completing this article, readers should be able to:

Describe the differential diagnosis of parathyroid diseases that result in hyper- and hypocalcemia.
Delineate the approach to making the diagnosis of parathyroid diseases and necessary therapies.

Introduction

Parathyroid hormone (PTH) is a peptide hormone that is the primary regulator of calcium concentrations in the bloodstream. PTH is released in response to a variety of signals, most importantly in response to low serum calcium concentrations. As a true hormone, it travels through the bloodstream to target tissues, primarily in the bone and kidney, where it has a variety of effects that serve to increase serum calcium, thus providing a correction for the original stimulus for release. PTH serves as an important regulator of bone turnover and in different settings can have either anabolic or catabolic effects in bone. Although PTH can mobilize phosphorus and calcium in bone, it also increases phosphate excretion, resulting in a net lowering of phosphate concentrations in the bloodstream. Given its central role in this important homeostatic process, a number of disorders are caused by abnormalities of PTH function.

Biochemistry

PTH is an 84-amino acid protein, with the first 34 amino acids being essential for full activity. (1) PTH signals through a G-protein-coupled receptor. (1) PTH shares this receptor with another peptide, PTH-related peptide (PTHrP), which is a paracrine factor that has important functions throughout the body, including regulation of the growth plates. That 2 peptides share the same receptor becomes important when …