RT Journal Article SR Electronic T1 Incidentally discovered severe hypercalcaemia from a functioning parathyroid cyst: the limitations of intraoperative parathyroid hormone (IOPTH) monitoring JF BMJ Case Reports JO BMJ Case Reports FD BMJ Publishing Group Ltd SP e239119 DO 10.1136/bcr-2020-239119 VO 14 IS 5 A1 Nogues, Juan Carlos A1 Cox, Robert A1 Mulcahy, Collin A1 Benito, Daniel A1 Goodman, Joseph YR 2021 UL http://casereports.bmj.com/content/14/5/e239119.abstract AB Parathyroid cysts (PCs) are rare pathologies and are typically non-functional (do not secrete parathyroid hormone (PTH)). The aetiology of PCs is highly debated, and management is complex. We present a unique case of a parathyroid adenoma contained within a functional PC and highlight the limitations of intraoperative PTH monitoring during the surgical resection of functional PCs.