SAT-386 Inconsistent Bilateral Arm Serum PTH Testing in Recurrent Hyperparathyroidism in a Patient Status-Post Parathyroid Auto-Transplantation

Background: More than 95% of patients with primary hyperparathyroidism will be cured with the initial operation by an experienced surgeon. However, localization of hyperparathyroid recurrences, especially after extensive surgery becomes challenging. For patients with transplanted parathyroid glands into the forearm, there may be utility in bilateral arm serum PTH testing to help with localization. Clinical Case: A 65-year-old woman presented to the clinic with primary hyperparathyroidism in 2008. After a localization study, she had a partial parathyroidectomy but continued to have persistent biochemical hyperparathyroidism despite negative localization studies. She was then referred to another institution for further studies. Follow up Sestamibi scans were negative but 4D-CT scans assisted in localizing the presence of a superior parathyroid gland adenoma which was later removed in 2011. During this time, the left inferior parathyroid gland was auto-transplanted into the left forearm. Again, her calcium and PTH levels rose despite negative Sestamibi scans showing no abnormalities in post-operative beds or in the forearm. Review of previous labs revealed elevated PTH levels in the ranges of 80-110 pg/mL since 2012-2019. The patient’s most recent PTH was 2408 pg/mL. At that point, the decision was made to repeat the labs on the left and right forearms simultaneously and labs showed PTH levels of 1283 pg/mL and 118 pg/mL, respectively. Repeat Sestamibi scan following these labs demonstrated evidence of increased radiotracer uptake in the region of the prior transplanted parathyroid tissue with no neck uptake concerning for hyperparathyroidism due to auto-transplanted hyperplastic tissue. Conclusion: This case demonstrates the utility of bilateral arm serum PTH testing in the evaluation of recurrent hyperparathyroidism in patient’s status-post parathyroid auto-transplantation.