SAT-LB086 Hungry Bone Syndrome Post Thyroidectomy in a Patient with Uncontrolled Grave Disease

Case: A 17-year-old girl presented to our office for a second opinion. She was diagnosed with hyperthyroidism at age 15 by an outside endocrinologist. She was initially treated with methimazole which was switched to PTU 100 mg 3 times a day due to a skin rash. She had poor compliance due to insurance problems. On examination, she had tachycardia (98/min) and hypertension (134/63 mm Hg). She had a significantly enlarged thyroid gland with a bruit. Atenolol 25 mg daily was added and PTU continued. Labs obtained by us confirmed severe hyperthyroidism with TSH less than 0.006 mIU/ml, free T4 greater than 7.7 ng/dL and a T3 greater than 650 ng/dL. Her TSI (504%), anti-thyroglobulin and anti-TPO antibodies were positive. 6 weeks later, the free T4 improved to 3.7 ng/dL. She then underwent total thyroidectomy and received Lugol iodine 3 days pre-op. Postoperatively, she developed persistent hypocalcemia (6.8 mg/dl with normal serum albumin) , hyperphosphatemia (6.5 mg/dl) and hypomagnesemia (1.1mg/dl) requiring treatment with IV calcium gluconate drip followed by high doses of oral calcium supplementation, oral calcitriol and oral magnesium supplementation to keep her serum calcium at the lower end of normal range. Her 25 (OH) vitamin D was low at 21 ng/ml. Additionally, she required intermittent IV calcium gluconate boluses for symptomatic hypocalcemia. Interestingly, post op iPTH was low but not in line with the severity of hypocalcemia (14.9-17pg/ml). Postoperative pathology report indicated presence of 3 parathyroid glands within the thyroid gland. She was discharged home on 6 gm of elemental calcium per day, 3.5 mcg calcitriol daily and 800 mg of magnesium oxide twice daily with a discharge serum calcium at 9 mg/dl after an 8 day hospital stay. After discharge, the calcium supplementation was further increased to 8 gm of elemental calcium per day and calcitriol and magnesium oxide were continued at the same doses. 6 months later, she was on 4gm elemental calcium per day with a low normal serum calcium and an iPTH between 15 and 17 pg/ml. Hungry bone syndrome (HBS) complicating hypoparathyroidism was suspected in our patient due to the unusually high doses of calcium supplementation required to maintain eucalcemia. HBS has been described after thyroidectomy in patients with severe or long standing hyperthyroidism. Increased bone turnover pre-op secondary to excess thyroid hormone is the suspected pathogenesis. It is also typically associated with hypophosphatemia which was not seen in our patient likely due to the underlying hypoparathyroidism. HBS is treated with high doses of calcium and calcitriol supplementation. Conclusion: HBS may be seen post-thyroidectomy in patients with severe hyperthyroidism. It should be suspected in patients with severe hypocalcemia requiring unusually high doses of calcium and calcitriol supplementation, not in line with the degree of hypoparathyroidism. Unless otherwise noted, all abstracts presented at ENDO are embargoed until the date and time of presentation. For oral presentations, the abstracts are embargoed until the session begins. Abstracts presented at a news conference are embargoed until the date and time of the news conference. The Endocrine Society reserves the right to lift the embargo on specific abstracts that are selected for promotion prior to or during ENDO.