FRI697 Severe Hypocalcemia Due To Idiopathic Hypoparathyroidism In An Elderly Female

Disclosure: K.A. Chopra: None. Most cases of acquired hypoparathyroidism in adulthood occur after neck surgery or radiation. However, idiopathic cases, although rare, do occur in elderly patients and should be a diagnosis of exclusion after thorough investigation. 76-year-old female with a history of chronic kidney disease, anemia of chronic disease, and hypertension presented with fatigue. Labs showed calcium (Ca) 5.7(RR 8.4-10.2 mg/dL), albumin 3.5(RR 3.5-5 g/dL), magnesium 2(RR 1.6-2.5 mg/dL), phosphorus 7.8(RR 2.5-4.4 mg/dL), parathyroid hormone 9(RR 15-75 pg/mL), 25-hydroxyvitamin D 32(RR 12-99 ng/mL). Patient denied history of neck surgery or radiation. Patient denied nephrolithiasis, perioral numbness, paresthesias, family history of hypoparathyroidism. Physical exam notable for positive Chvostek sign. Neck ultrasound unremarkable, no evidence of infiltrative disease. Urine Ca was low at 6 mg/24 hour(RR 100-300 mg/24hr). ACE level 10 nmol/ml/min(RR<40 nmol/ml/min) and 1,25 dihydroxyvitamin D level 12(RR 18-78 pg/mL) making sarcoidosis or granulomatous disease unlikely. HIV screen negative and interferon gamma response to mycobacterium tuberculosis antigens was not detected. Ferritin elevated at 300(RR 12-150 ng/mL) but transferrin saturation was 15%(RR 15-55%), not consistent with hemochromatosis. Antiparathyroid antibodies were negative. Patient denied mucocutaneous candidiasis, however testing for underlying autoimmune polyglandular syndrome type 1 (APS type 1) and adrenal insufficiency was completed with cosyntropin stimulation test. Patient had normal response to cosyntropin with baseline cortisol 20.1 (RR 6-18.4 ug/dL) and ACTH 37.7(RR<52 pg/mL), 30 minute cortisol 27(RR 6-18.4 ug/dL) and 60 minute cortisol 37(RR 6-18.4 ug/dL). Patient was treated with Ca gluconate infusion (100 ml of 10% Ca gluconate in 1000 mL of normal saline) at 30 ml/hr and Ca level gradually improved. Once Ca level was greater than 8.0(RR 8.4-10.2 mg/dL), Ca drip was discontinued. Due to patient’s lack of prior neck surgery history, lack of evidence of infiltrative conditions, negative antiparathyroid antibodies, normal adrenal function (unlikely APS type 1), lack of family history, and low urine Ca (unlikely activating mutation of Ca sensing receptor), patient’s hypoparathyroidism was considered idiopathic. Patient was discharged on oral Ca carbonate, Ca acetate, and calcitriol tablets. On follow up, patient had Ca 8.5(RR 8.4-10.2 mg/dL) with symptom improvement. Although hypocalcemia is commonly encountered, it is rare to see severe hypocalcemia in an elderly patient due to hypoparathyroidism without a history of neck surgery or radiation. Therefore, it is vitally important to conduct a thorough investigation to rule out underlying causes before diagnosing idiopathic hypoparathyroidism as highlighted in our case to guide future treatment and optimize patient health. Presentation: Friday, June 16, 2023