Autonomous Hyperparathyroidism Following Long-term Phosphate Treatment for Tumor-Induced Osteomalacia: Case Report and Review of the LiteratureTournis, Symeon MD*; Samdanis, Vasilios MD*; Economopoulos, Dimitrios MD*; Giannikou, Panagiota MD*; Lyritis, George P. MD, PhD†Author Information *Research Fellow, †Professor of Orthopaedics and Director, Laboratory for Research of Musculoskeletal System, University of Athens, KAT Hospital, Athens, Greece. The authors have disclosed that they have no significant relationships with or financial interests in any commercial company that pertains to this educational activity. Lippincott Continuing Medical Education Institute, Inc. has identified and resolved all faculty conflicts of interest regarding this educational activity. Reprints: Symeon Tournis, MD, Laboratory for Research of Musculoskeletal System “Th. Garofalidis,” University of Athens, KAT Hospital, 10 Athinas str., Kifissia, PC: 14561, Athens, Greece. E-mail: [email protected] Chief Editor's Note: This article is the 25th of 36 that will be published in 2007 for which a total of up to 36 AMA PRA Category 1 Credits™ can be earned. Instructions for how credits can be earned precede the CME Examination at the back of this issue. The Endocrinologist: September/October 2007 - Volume 17 - Issue 5 - pp 263-266 doi: 10.1097/TEN.0b013e3181514e2b Buy Take the CME Test Metrics Abstract Development of secondary or even tertiary hyperparathyroidism following phosphate administration is an established complication in patients with X-linked hypophosphatemic rickets. However, in tumor-induced osteomalacia (TIO) there are very few documented cases of hyperparathyroidism persisting even after excision of the tumor (tertiary hyperparathyroidism). The development of hyperparathyroidism in TIO is related to long-term phosphate administration, which represents the main treatment option in cases of unlocalized or nonexcisable tumors. Furthermore, low or inappropriately normal calcitriol levels either systemically or at the level of parathyroid cell are probably implicated in parathyroid tumorigenesis. We present a case of a 68-year-old female patient with TIO who received long-term phosphate treatment prior to localization and excision of the tumor and afterward developed autonomous hyperparathyroidism. © 2007 Lippincott Williams & Wilkins, Inc.