8025 Hypocalcemia Secondary To Relative Hypoparathyroidism After Parathyroidectomy For Tertiary Hyperparathyroidism

Abstract Disclosure: N.N. Solanki: None. M.A. Bahrou: None. W. Taha: None. Parathyroidectomy is one of the treatment options for patients with tertiary hyperparathyroidism. Hypocalcemia following parathyroidectomy is a well-known occurrence due to a sudden drop in parathyroid levels, commonly to normal levels. We describe a case of hypocalcemia following subtotal parathyroidectomy for tertiary hyperparathyroidism with elevated parathyroid hormone (PTH) levels but relatively low compared to baseline. A 56-year-old female with a history of end-stage renal disease status post renal graft rejection presents for elective parathyroidectomy for tertiary hyperparathyroidism. Pre-operative investigations showed serum calcium levels of 11.6 mg/dL, normal value (NV): 9-10.5 mg/dL, serum phosphorus levels of 5.6 mg/dL, NV: 2.7-4.5 mg/dL, very high levels of serum intact PTH of 1257 pg/mL, NV: 10-65pg/mL and high level of alkaline phosphatase of 376 U/L, NV: 40-150 U/L. The patient underwent right and left inferior parathyroidectomy. Postoperatively, the patient's intact PTH levels remained elevated [895 pg/mL]; however, they decreased compared to baseline, but she developed hypocalcemia requiring intravenous and oral calcium supplementation. On postoperative day seven, she was discharged on oral calcitriol and calcium carbonate. Hypocalcemia following parathyroidectomy is well-described in cases where the PTH levels drop to the normal range. This case highlights that hypocalcemia can also occur when there is a relatively lower PTH level while the absolute value remains elevated. Presentation: 6/1/2024