PARATHYROID CARCINOMA AND INCIDENTAL FINDING OF HASHIMOTO'S THYROIDITIS

Abstract

INTRODUCTION
Parathyroid carcinoma is a very rare endocrine neoplasia. The incidence reported is less than 1% in primary hyperparathyroidism. The presence of this rare carcinoma is even less likely in the setting of chronic kidney disease. Unfortunately, parathyroid carcinoma is difficult to differentiate clinically with parathyroid adenoma and hyperplasia pre-operatively.

CASE
A 48-year-old male, diagnosed with end-stage renal disease secondary to IgA nephropathy and maintained on chronic hemodialysis for 8 years, presented with progressive decreasing height and occasional bone pain. Despite compliance to hemodialysis, calcimimetics, phosphate binders, calcium and vitamin D supplementation to suppress the high PTH levels, he remained persistently hyperparathyroid with intact PTH of 4793 pg/ml (NV: 15-65 pg/ml). Other laboratory findings showed vitamin D sufficiency (Vitamin D 87 nmol/L (NV: >75 nmol/L), hypocalcemia (ionized calcium 1.08 mmol/L (NV: 1.10-1.35) and hyperphosphatemia (inorganic phosphate 2.15 mmol/L (NV: 0.01-1.45 mmol/L). With the failure of medications to suppress the high PTH levels, surgical removal of the parathyroid glands was the next plausible option. A dual phase sestamibi scan of the parathyroid revealed a single focal activity at the mid aspect of the right thyroid bed on the wash-out phase. He subsequently underwent total parathyroidectomy and total thyroidectomy. Intraoperative findings revealed enlarged bilateral parathyroid glands with the largest measuring 2x2 cm and incidental findings of multiple nodules in both thyroid lobes. Histopathology revealed parathyroid carcinoma in 3 out of 4 glands and Hashimoto’s thyroiditis with multinodular adenomatous goiter.

CONCLUSION
It is a challenge to clinically differentiate parathyroid carcinoma and other causes of hyperparathyroidism among patients undergoing chronic maintenance hemodialysis due to the effect of renal insufficiency on calcium metabolism. This case highlights an unusual case of parathyroid carcinoma in a patient with ESRD and incidental finding of Hashimoto’s thyroiditis, who presented with extremely elevated intact parathyroid hormone accompanied by hypocalcemia.