8157 Hypercalcemia To Hypocalcemia In Three Days: The Importance Of Asking The Questions

Abstract Disclosure: P. Kachhadia: None. K. Patel: None. S. Khan: None. A. Abu Limon: None. S. Aldasouqi: None. F. Akanbi: None. Z. Ul Abideen: None. Introduction: Severe hypercalcemia needing inpatient hospitalization requires very thorough history taking in order to determine etiology and treatment plan. Causes differ drastically, and misdiagnosis or mistreatment can be life threatening. Here, we present a case of symptomatic hypercalcemia secondary to milk-alkali syndrome that was treated promptly after admission with IV zoledronic acid, leading to severe symptomatic hypocalcemia and prolonged hospitalization. Case presentation: Patient is a 68 year old female with a PMH of breast cancer, osteoporosis and hiatal hernia who presented to the emergency department for fatigue, constipation and lightheadedness. On evaluation, she was found to have a creatinine of 1.54 (0.6-1.1 mg/dL), eGFR 36 (>90 mL/min/1.73 m²), Ca 18.48 (8.6-10.2 mg/dL), albumin 4.7 (3.4-5.4 g/dL), Mg1.4 (1.7-2.2 mg/dL), 25-OHD 18 (30-100), 1,25-Dihydroxy Vitamin D 7.4 (18-78 pg/mL), PTH 11.2 (15-65 pg/mL), phosphorus level 2.4 (2.5-4.5mg/dL), TSH 2.01 (0.4-4.0 mIU/L). SPEP and PTHrP were unremarkable. Due to history of prior breast cancer, imaging was done and CT showed new possible RUL pancoast tumor with RUL spiculated opacity. Patient was started on IV fluids and subsequently received IV zoledronic acid due to concern for severe hypercalcemia secondary to malignancy. By day 3 of treatment, patient's calcium decreased severely, down to a corrected calcium level of 6.4 (8.6-10.2 mg/dL). It was upon further investigation and discussion with the patient that we discovered the patient had received subcutaneous denosumab for her osteoporosis three weeks prior to admission. In addition, she was taking six tums daily (total 1 month duration) for symptoms of dyspepsia secondary her hiatal hernia. The patient’s severe hypocalcemia was treated with high dose oral calcium carbonate and vitamin D along with IV calcium gluconate. Magnesium was replaced daily. Through daily replacement, patient was kept in the hospital for a total of 10 days duration before her calcium levels were deemed safe for return home. Discussion: Hypercalcemia is a common cause of hospitalization worldwide. Testing should be comprehensive and history taking should be thorough to help navigate treatment plans. Bisphosphonates are indicated for hypercalcemia of malignancy, and its use otherwise may be the cause of severe hypocalcemia if not used in the right setting. In our case, the patient’s hypocalcemia was multifactorial from prior denosumab use and then subsequent zoledronic acid use. Additional risk factors included low vitamin D counts and disruption of high amounts of over the counter tums after being admitted to the hospital. Anchoring bias also led clinicians to believe that the hypercalcemia was secondary to malignancy. Consequently, this led to a prolonged 10 day hospitalization for persistently low calcium levels. Presentation: 6/1/2024