SAT-756 Parathyroid Venous Sampling-Guided Diagnosis and Surgical Resolution of Persistent PrimaryHyperparathyroidism

Abstract Disclosure: A. Sood: None. L. Sayyed Kassem: None. Background: Persistent primary hyperparathyroidism (PHPT) presents a diagnostic and management challenge,especially when imaging fails to localize ectopic or supernumerary parathyroid tissue. This case highlights thepivotal role of parathyroid venous sampling in guiding successful surgical intervention.Case Description: A 34-year-old female presents with hypercalcemia 10 years after her initial diagnosis with PHPTand 4 years after 4-gland exploration and left lower parathyroidectomy. Surgical pathology had shown normalparathyroid tissue, and she was lost to follow up after displaying delayed and transient resolution ofhypercalcemia. Current evaluation confirms recurrence/residual PHPT with serum Ca of 11.4 mg/dL,inappropriately elevated PTH of 91 pg/mL, elevated urinary calcium excretion and low bone density accompaniedby fatigue and cognitive dysfunction. Following unremarkable neck ultrasonography and (99mTc) sestamibi scan,4D CT scan suggested the presence of a right parathyroid adenoma. Right neck exploration was performed, andone parathyroid gland was removed and partially reimplanted. Hemithyroidectomy was also performed in case ofintrathyroidal adenoma. Surgical pathology did not reveal parathyroid pathology, and hypercalcemia persistedpost-operatively. Peripheral venous sampling (PVS) was pursued, which revealed markedly elevated PTH levels(300 pg/mL) in the left brachiocephalic vein only, strongly suggesting an ectopic adenoma. Re-exploration with leftcentral neck dissection did not show gross pathology intra-operatively but resulted in > 80% PTH drop, and surgicalpathology confirmed parathyroid adenoma in the central neck compartment. Postoperatively, biochemicalnormalization of PTH ( < 4 pg/mL) was achieved and hypocalcemia developed, for which she was started oncalcium supplements and calcitriol.Discussion: This case illustrates the not infrequent challenge of localizing parathyroid adenomas where negative ormisleading imaging modalities could result in unsuccessful surgery. In this instance, PVS was the sole modality thatcorrectly identified the location of the adenoma and yielded a positive surgical outcome for a young patient withsymptomatic HPTH. This outcome is in line with prior literature demonstrating enhanced surgical outcomes whenlocalization efforts are augmented with PVS in imaging-negative or -discordant cases. Conclusion: The integration of innovative diagnostic tools, such as PVS with meticulous surgical intervention can behighly valuable in the management of recurrent primary hyperparathyroidism Presentation: Saturday, July 12, 2025