Endocrine Abstracts

Background: Parathyroid carcinoma is a rare cause of primary hyperparathyroidism. There’s an overlap between benign and malignant disease clinical presentation, but the presence of very high calcium levels (>14 mg/dl), markedly raised levels of PTH, palpable neck mass or severe bone/kidney disease is more common in parathyroid carcinoma. We present a case of primary hyperparathyroidism due to a parathyroid carcinoma, with unusual presentation.

Case: A 75 years-old male was referred to the Endocrinology department to evaluate hypercalcemia, identified during the study of alithiasic acute pancreatitis. The patient had a previous history of pre-Diabetes, arterial hypertension and chronic kidney disease. During the previous hospitalization, a pancreatic mass and pelvis bone lesions were noticed in the abdominal CT. A FDG-PET was performed, with uptake at both locations. There was a suspicion of pancreatic malignant disease, with bone metastasis, but the bone biopsy was compatible with brown tumors and the pancreatic mass biopsy was benign. Laboratory tests showed a calcium level at presentation of 12.9 mg/dl (8.8-10.2), with a phosphate of 2.4 mg/dl (2.5-4.5), PTH level of 357 pg/ml (normal range 15-65) and an estimated glomerular filtration rate of 38 ml/min/1.73 m². After vigorous hydration and intravenous Pamidronate, a reduction of calcium to basal levels of 10.6 – 11.4 mg/dl was noticed in the following months. Primary hyperparathyroidism was assumed, with bone disease (brown tumors at pelvis) and kidney disease (lithiasis and chronic kidney disease). Cervical ultrasonography and CT showed a mixed nodule with 34×24×22 mm at the inferior pole of right thyroid lobe, concordant with sestamibi scintigraphy result. The patient had selective parathyroidectomy with a low normal intraoperative PTH level. Postoperatively, the patient had a low normal calcium/hypocalcemia, corrected with calcitriol and oral calcium. Histology was malignant (parathyroid carcinoma). Two years after surgery, the patient has normal calcium and phosphate and a secondary hyperparathyroidism due chronic kidney disease (latest laboratory results: calcium 9.2, phosphate 3.2, PTH 75, glomerular filtration rate of 28 ml/min/1.73m²) without signs of recurrence of the disease.

Discussion: Parathyroid carcinoma is a challenging entity, with various clinical presentations. In our case, calcium level at presentation (12.9 mg/dl), basal calcium after bisphosphonates (10.6-11.4) and PTH levels were not suspicious of malignant disease. However, the patient had severe target organ involvement – chronic kidney disease, lithiasis, brown pelvis tumors and acute pancreatitis – that are more frequent in malignant disease.