8732 Hypercalcemia: When It’s Not PTH, Why Not Blame Your Neighbor?

Abstract Disclosure: D. Misra: None. M.R. Brennan: None. L. Misra: None. A 60-year-old female with a history of recently diagnosed hyperthyroidism, hypertension, and seizure disorder presents with a four-month history of neck swelling and pain. The patient was diagnosed with hyperthyroidism four months prior to admission and was started on methimazole 10 mg three times a day for two months, then instructed to decreased to 10 mg daily. In addition to the four months of neck swelling and pain, the patient also endorsed difficulty swallowing, palpitations, constipation, and bilateral ankle edema. Vital signs were stable other than a heart rate in the low 100s. Physical exam revealed a fixed painful L sided neck mass with no signs of airway compromise and bilateral exophthalmos. Labs revealed TSH <0.01 uIU/mL, Free T4 2.1 ng/dL, TSI was elevated (>40) IU/L. potassium 3.2 mmol/L, hypomagnesemia 1.3 mg/dL, troponin of 55 ng/l and hemoglobin 9.3 g/dL. The patient had a calcium of 10.6 mg/dL and an ionized calcium of 5.73 mg/dL with a normal PTH (34 pg/mL) and a low Vitamin D (22 ng/mL). A CT of the neck was performed showing marked thyromegaly with innumerable subcentimeter hypodense nodules in both lobes and a dominant 1.1 nodule in right lobe. Initial therapy involved correction of the electrolytes, telemetry monitoring, and a consultation to the endocrine service. The endocrine team started the patient on methimazole 10mg/daily and ordered a thyroid scan. Scintigraphy was performed and was consistent with Graves’ disease. On Day #2 the patient’s vital signs had normalized and the patient was able to swallow and tolerate a regular diet, The scan showed an enlarged thyroid with diffuse nodular character and moderate hyperemia consistent with diffuse thyroiditis. The scan also described a multinodular goiter with the largest nodule measuring 2.2 cm. She was discharged on Day #3 on methimazole 10mg daily and asked to follow up with endocrinology. Graves’ disease is a common cause of hyperthyroidism and is caused by autoantibodies that increase the production of thyroid hormone. Along with classic symptoms of hyperthyroidism, our patient had hypercalcemia. This was non-PTH mediated and in the absence of other signs or symptoms of a malignancy or granulomatous process, the hypercalcemia is likely due to her hyperthyroid state. Hyperthyroidism-associated hypercalcemia is a rare complication in hyperthyroid patients but should not be forgotten when evaluating non-PTH mediated hypercalcemia as it can be corrected easily with appropriate medications or in this case with the correction of the hyperthyroidism. Consideration of this etiology may also reduce the number of extraneous labs and imaging when no other common etiology is found. Presentation: 6/2/2024