Abstract Disclosure: R. Rani: None. C. Mullarkey-desapio: None. Introduction: Hungry Bone Syndrome (HBS) is a rare yet severe complication following parathyroidectomy, characterized by pronounced hypocalcemia subsequent to a rapid decline in parathyroid hormone (PTH) levels. Renal hyperparathyroidism (RHPT) carries a heightened risk of HBS compared to primary hyperparathyroidism (PHPT), with prevalence varying from 15% to 25% in PHPT to as high as 75-92% in RHPT. This elevated risk in RHPT is attributed to chronically elevated PTH levels, both in terms of duration and intensity as compared to PHPT. Preoperative predictors for HBS occurrence and severity include younger age, larger gland size, lower preoperative calcium levels, elevated bone turnover markers, and the magnitude of PTH elevation. Case Report: We present a case of a 36-year-old female with End-Stage Renal Disease (ESRD) requiring dialysis, complicated by renal osteodystrophy and a radial fracture, unresponsive to medical therapy, who was admitted for parathyroidectomy. Preoperative labs revealed calcium at 8.3 mg/dL, phosphate at 4.1 mg/dL, alkaline phosphatase (ALP) at 797 IU/L, and an extremely elevated parathyroid hormone (PTH) level at 4139 pg/ml. Within 24 hours of parathyroidectomy (three and a half glands were removed, the largest weighing 0.7gm), her PTH levels declined to the 130s, accompanied by symptomatic hypocalcemia (calcium 6.5mg/dL). Initial management involved intravenous calcium gluconate and subsequent high-dose oral calcium (up to 10-16gm daily) with Calcitriol 1 mcg twice daily. Despite repletion, her calcium levels remained low on postoperative day 4 (calcium 6.8mg/dL, phosphate 1.9 mg/dL, magnesium 1.7mg/dL) with PTH at 131 pg/ml, confirming Hungry Bone Syndrome. After seven days of aggressive intravenous and oral calcium supplementation with high-dose Calcitriol, she was discharged with a calcium level of 8.9mg/dL. Discussion: Management of HBS following renal hyperparathyroidism surgery presents significant challenges due to associated comorbidities and other electrolyte abnormalities, with limited literature providing guidance on prevention and management. Our case demonstrated that early suspicion and aggressive management improved patient outcomes. Suspecting HBS in high-risk individuals and initiating interventions pre and post-surgery, including pre-treatment with calcitriol, bisphosphonates, and early aggressive intravenous calcium supplementation post-surgery, could potentially reduce morbidity and length of hospital stay. Presentation: 6/1/2024