E1480. The Overactive Parathyroid Glands: Go Above and Beyond the Expected!
  1. Pei Ing Ngam; National University Hospital
  2. Tang Yu Lin; Singapore General Hospital
  3. Wei Ming Chua; Singapore General Hospital
Hyperparathyroidism is an endocrine disorder caused by one or more hyperfunctioning parathyroid glands (PTGs). Parathyroid imaging is used for identification and localization of the hyperactive PTG(s), and not for diagnosis of hyperparathyroidism. Parathyroid scintigraphy and ultrasonography of the neck are commonly used for this purpose.

Educational Goals / Teaching Points
The objectives of this article are to depict the embryology and anatomy of PTGs, explain the physiologic principles of parathyroid scintigraphy and describe the various imaging methods, illustrate the classic and atypical presentations of parathyroid pathologies, and highlight potential pitfalls when interpreting the imaging findings.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
We illustrate the embryology of the PTGs and their anatomical variants. The classic locations of superior and inferior PTGs ectopy as well as incidence of supernumerary PTGs are also discussed. PTGs are small glands consisting of chief, oxyphil, transitional oxyphil and water-clear cells. Hyperfunctioning PTGs, with abundance of oxyphil cells that are rich in mitochondria form the fundamental of radionuclide parathyroid imaging. The physiologic principles of mitochondria-based tracers used in parathyroid scintigraphy and their physiological distribution are discussed. We depict the three imaging techniques used for the detection of hyperfunctioning PTGs, namely single-phase dual-tracer subtraction imaging, dual-phase single-isotope imaging, and a combination of the two. The advantages and pitfalls of various imaging protocols and their classic imaging findings were discussed. In addition, we present a series of hyperfunctioning PTGs, depicting the spectrum of normal findings, location and patterns of various uptakes by parathyroid adenomas and hyperplasia, and common pitfalls in sestamibi imaging.

Parathyroid scintigraphy is the modality of choice for preoperative identification and localization of hyperfunctioning PTGs. A minimally invasive surgical approach is preferred and successful preoperative localization of the hyperfunction PTG(s) is important in facilitating this. We present an overview of parathyroid scintigraphy to assist the nuclear medicine and radiology resident or fellow in detecting and correctly localizing hyperfunctioning parathyroid lesions.