SAT-762 Resolution of Persistent Hypokalemia Following Parathyroidectomy in a patient with Primary Hyperparathyroidism.

Abstract Disclosure: A. Imran: None. F. Zhang: None. M.V. Perez Bastidas: None. K. Kodroff: None. Background: The correlation between the parathyroid hormone and Renin-Angiotensin-Aldosterone System (RAAS) was reported in animal study. While hyperkalemia post-parathyroidectomy has been noted in secondary hyperparathyroidism, the effect of parathyroidectomy on potassium homeostasis of primary hyperparathyroidism remains unclear.Clinical Case:A 64-year-old woman with hypercalcemia induced by primary hyperparathyroidism presented with elevated calcium (12.8 mg/dL), PTH (363.9 pg/mL), low potassium (3.0 mEq/L), and elevated renin activity (21.0 ng/ml/hr). Despite discontinuing Hydrochlorothiazide and starting Cinacalcet 30 mg daily, her potassium levels remained low at 3.3 mEq/L, although her calcium level improved. DEXA scanning showed lumbar spine osteoporosis and NM Parathyroid scan suggested a possible parathyroid adenoma. Deteriorating condition with hypercalcemia calcium (13.6 mg/dL), hypokalemia (2.9 mEq/L), and elevated PTH (690.7 pg/mL) necessitated hospitalization. Treatment with intravenous fluids and electrolytes improved her condition. Renal ultrasound was negative. She was discharged on Cinacalcet 60 mg twice a day and potassium supplements. Follow-up showed persistent hypercalcemia, hypokalemia, and elevated renin activity (16.136 ng/ml/hr). Parathyroidectomy confirmed parathyroid adenoma. Post-surgery, her calcium normalized to 7.8 mg/dL and PTH level improved to 99.4 pg/mL. Interestingly, her Potassium level and renin activity were also normalized. Adjustments were made to discontinue potassium supplements while continuing the angiotensin receptor blocker. Renin level on follow ups later increased again but the potassium level remained normal without potassium supplement. Conclusion: This is the first case report of hypokalemia resolved after parathyroidectomy in a patient with primary hyperparathyroidism. It highlighted the complex interaction between parathyroid hormone and RAAS; and also, parathyroid hormone’s calcium mediated direct effect in regulating potassium levels. Presentation: Saturday, July 12, 2025