SAT-379 Giant Parathyroid Adenoma

Giant parathyroid adenoma Background: Primary hyperparathyroidism is the most common cause of hypercalcemia. On ultrasound PTH adenomas are typically homogenous, hypoechoic, oval or bean-shaped with peripheral vascularity. Clinical Case: A 60 year old woman with a history of calcium oxalate nephrolithiasis presented with fatigue, worsening depression, body aches of 3 months duration. Labs showed a serum calcium 11.1 mg/dl (normal range 8.5–10.1 mg/dl), PTH 114.3 pg/ml (normal range 12–88 pg/ml), 25 OH Vitamin D 11 ng/ml (normal range above 29 ng/ml), alkaline phosphatase 137IU/L (normal range 27–120 IU/L), spot urine calcium 34.8 mg/dl, spot urine creatinine 92.1 mg/dl (estimated 24 hour urine calcium 415 mg/dl). She was started on Vitamin D 1000 IU daily. A PTH scan with SPECT/CT showed a right parathyroid adenoma and possible thyroid nodules. A neck ultrasound demonstrated a left 1.5 cm thyroid nodule and a right 3cm lesion. She underwent FNA of the left thyroid nodule and pathology was suggestive of a benign follicular nodule. She underwent parathyroid gland exploration with resection of the right lesion which was a 3.5 x 2.5 x 1.4 cm right superior 5.68 gm PTH adenoma. Postoperatively her serum calcium normalized to 10.1 mg/dl, PTH was 8.4 pg/ml, 25 OH vitamin D was 15 ng/ml. Her Vitamin D dose was increased. Clinical Lessons: A normal parathyroid gland typically weighs 30–60 mg and is 3–4 mm in size. The differential diagnosis for large parathyroid lesions is parathyroid carcinoma vs giant parathyroid adenoma. Although there is not a definitive size cutoff to define giant parathyroid adenomas, a size greater than 3.5 gm has been used (1). On ultrasound giant parathyroid adenomas are homogenous with smooth borders whereas parathyroid carcinomas are large lobulated heterogeneous hypoechoic lesions (2). A depth/width ratio on ultrasound may be the ultrasound parameter with greatest discriminatory capacity as a depth/width ratio greater than or equal to 1 had 94% sensitivity and 95% specificity for parathyroid carcinoma (2). Whether vitamin D deficiency is a risk factor for the development of large parathyroid glands is controversial as there has been conflicting data on this (1,3). Because there is no serum calcium level that distinguishes parathyroid carcinoma from a parathyroid adenoma neck ultrasound may be a helpful tool in evaluating these patients. References: 1. Spanhemier PM, Stoltze AJ, Howe JR, et al. Do giant PTH adenomas represent a distinct clinical entity? Surgery. 2013 Oct; 154(4):714–719. 2. Hara H, Igarashi A, Yano Y, et al. Ultrasonagraphic features of PTH carcinoma. Endocr J. 2001 April 48(2):213–217. 3. Rao DS, Honasoge M, Divine GW, et al. Effect of vitamin D nutrition on PTH adenoma weight: pathogenetic and clinical implications. J Clin Endocrinol Metab. 2000 Mar 85(3): 1054–1058.