SAT202 A Case Of Primary Hyperparathyroidism Secondary To Ectopic Intrathymic Parathyroid Adenoma

Abstract

Abstract Disclosure: S. Pandiri: None. Introduction: Primary hyperparathyroidism (PHPT) is the most common cause of hypercalcemia. Majority of cases are due to a single adenoma. In about 6-16% of cases, the parathyroid adenoma is in an ectopic location. Accurate preoperative imaging is key in localizing ectopic parathyroid adenomas. Clinical Case: 64 year old man with hypercalcemia was referred to endocrinology for further evaluation. His symptoms included fatigue, nausea, polydipsia and polyuria. There was no history of fractures, radiation therapy or family history of hypercalcemia. The patient’s past medical history is significant for nephrolithiasis, thyroid nodules and hypertension. He was started on Cinacalcet 30 mg, twice daily, by his primary care physician about 6 weeks prior to the initial visit. Physical exam was unremarkable. Lab studies were significant for elevated albumin-corrected calcium: 11.2 mg/dl (8.6-10.3 mg/dl), elevated PTH: 578.1 pg/ml (12-88 pg/ml), 25-OH vitamin D: 17 ng/ml (>30 ng/ml), phosphorus: 2 mg/dl (2.5-4.5 mg/dl) TSH: 0.54 mIU/L (0.40-4.50 mIU/L), 24 hr urine calcium: 429 mg (<250 mg/24 hr). The lab findings were consistent with hypercalcemia due to primary hyperparathyroidism. Neck Ultrasound showed bilateral thyroid nodules but no parathyroid adenoma. Tc-99m sestamibi scintigraphy was significant for 2.8 x 1.5 x 3.4 cm mass in the anterior mediastinum but did not show uptake in the neck. CT Neck showed a mass in the anterior mediastinum measuring 1.6 x 2.7 cm. Bone density was significant for osteopenia. He underwent robot assisted mediastinal mass excision two months after the initial evaluation. The pathology was significant for ectopic, intrathymic parathyroid adenoma, watery cell type with nuclear atypia, measuring 3.8 x 3.1 x 1.3 cm. Labs at the follow up visit showed normal albumin-corrected calcium of 8.6 mg/dl, improved PTH of 110.3 pg/ml. His symptoms improved significantly after surgery. Conclusion: This case demonstrates that preoperative localization of an ectopic parathyroid adenoma can prevent recurrent surgeries and persistent hypercalcemia. It is important for physicians to be aware of the various ectopic locations of parathyroid adenomas during the diagnostic workup of PHPT. Reference: Roy M, Mazeh H, Chen H, Sippel RS. Incidence and localization of ectopic parathyroid adenomas in previously unexplored patients. World J Surg. 2013 Jan;37(1):102-6. doi: 10.1007/s00268-012-1773-z. PMID: 22968537. Presentation: Saturday, June 17, 2023