SAT193 Double Trouble: A Case of Ipsilateral Double Parathyroid Adenoma

Disclosure: J.P. Suelto: None. G.D. Wassmer: None. Background: Eighty percent of the cases of Primary Hyperparathyroidism is caused by a single adenoma and only about 15% are multiglandular adenoma. Parathyroid imaging like Sestamibi is less sensitive in detecting multiglandular disease. Clinical Case: A 63 year-old female presented with intermittent left lower back pain for 7 years. There was no joint pain, weakness, urinary symptoms, constipation and abdominal pain. In 2019, due to persistence of left back pain, abdominal ultrasound done showed a right non-obstructing nephrolithiasis. Ionized and total calcium were elevated at 1.53 meq/L (NV 1.12-1.32 meq/L) and 11.35 ng/dl (NV 8.42-10.23 ng/dl) respectively with normal creatinine, phosphorus and albumin. PTH was elevated at 116.6 pg/ml (NV 10-65 pg/ml). Primary Hyperparathyroidism probably secondary to parathyroid adenoma was considered. Thyroid ultrasound showed right thyroid cyst but no enlarged parathyroid gland. Parathyroid imaging using Dual Isotope Subtraction Method neither showed evidence of adenoma. Patient was advised parathyroidectomy but did not consent hence started on Cinacalcet. In 2021, ionized calcium was still elevated to 1.58 meq/L with elevated PTH 151 pg/ml and low Vitamin D level 22.76 ng/ml (>30 ng/mL). Patient was given Vitamin D3 2000 IU daily and Cinacalcet was up-titrated to 60mg daily. Sestamibi/SPECT CT showed faint focus of radioactivity in the right thyroidal bed area suspicious for parathyroid adenoma or hyperplasia. She then agreed to have parathyroidectomy. There was no decrease in PTH after removal of the right inferior parathyroid gland (measuring 1.8x0.6x0.6cm, weighs 500mg), hence re-exploration was done. It was only after the removal of the right superior parathyroid gland (measuring 2.8x0.9x0.7cm, weighs 1 gram) when the 5 and 10 minute post excision PTH decreased to 123.91 and 76.01 pg/ml respectively from preincision PTH of 407.19 pg/ml. Histopathology showed Parathyroid adenoma of right inferior and superior parathyroid glands. No further evidence of hypercalcemia was noted at 6-month follow-up. Conclusion: Double adenoma is reported in 2% to 12% of patients with primary hyperparathyroidism. This occurs predominantly as bilateral superior in 45% and on same side of the neck in 18%. Sestamibi scanning is poor in the presence of multiglandular disease. It was observed that the presence of oxyphil cells may cause longer sestamibi retention in parathyroid tissues. Given the same amount of oxyphil cells in ipsilateral adenomas, the tracer may be distributed hence faintly seen on imaging. Addition of SPECT/CT/4D CT may improve the anatomical localization. Another reason for false negative imaging in this patient can be due to use of Cinacalcet which may decrease scintigraphy uptake of parathyroid adenoma. The combination of preoperative imaging localization and intraoperative PTH monitoring permits successful surgical outcome. Presentation: Saturday, June 17, 2023