A GIANT PARATHYROID ADENOMA

Abstract

INTRODUCTION/BACKGROUND
Giant parathyroid adenomas, defined as adenomas weighing >3.5 gm, are rare, comprising a small fraction of all parathyroid adenomas. We describe a patient who presented with a giant parathyroid adenoma and markedly elevated parathyroid hormone.

CASE
A 57-year-old male, with a family history of adrenal Cushing’s syndrome and hyperthyroidism, was incidentally diagnosed with primary hyperparathyroidism during admission for cerebral infarction, with hypercalcemia (3.2 mmol/L), elevated intact parathyroid hormone (iPTH) (140.2 pmol/L), and vitamin D deficiency (46 nmol/L). He was treated with saline diuresis, subcutaneous denosumab 60 mg, and subcutaneous calcitonin 200 U BD, but defaulted to further workup. Nine months later, he returned with altered sensorium, hypercalcemia (3.43 mmol/L) and elevated iPTH (448.9 pmol/L), the same treatment was given as in the previous admission. Ultrasound of the parathyroid showed an interior hypoechoic lesion measuring 2.0 x 2.6 x 3.2 cm. Tc-99m Sestamibi scan suggested a left inferior parathyroid lesion without an ectopic tissue. DXA scan showed osteoporotic changes in the distal third radius and femoral neck. KUB Ultrasound showed no renal calculi. One month later he was admitted for hypercalcemia and acute kidney injury, treated with saline diuresis and subcutaneous denosumab 120 mg, and eventually underwent left inferior parathyroidectomy with intraoperative iPTH monitoring. From his highest preoperative iPTH at 828 pmol/L, a reduction to 236.7 pmol/L was seen at 10-minutes post-incision. Intra-op findings showed a large left inferior parathyroid tumour, measuring 3.5 x 2.7 x 2.0 cm, weighing 14 gm. Histopathology was consistent with parathyroid adenoma. He was started on calcitriol and calcium carbonate post-operatively and did not develop hungry bone syndrome.

CONCLUSION
In giant parathyroid adenomas, a disproportionate rise in serum iPTH may result from factors like vitamin D deficiency, chronic iPTH elevation, or resistance to physiological effects of PTH. Distinguishing them from parathyroid carcinoma is challenging due to shared high iPTH and calcium levels, though studies showed that giant parathyroid adenomas may be asymptomatic. Histopathological examination is essential for diagnosis, warranting early surgical removal.