Parathyroid Carcinoma with Low Values of Elevated Parathyroid Hormone: A Case Report

Parathyroid Carcinoma (PC) is a rare endocrine malignancy, accounting for <1% of sporadic Primary Hyperparathyroidism (PHPT) cases. A preoperative and even intraoperative diagnosis of PC is rarely reported due to its close resemblance to parathyroid adenoma with respect to symptoms- hypercalcaemia, renal stones and/or failure, osteoporosis, and cardiac/neurocognitive dysfunction. The mean serum calcium in PC is reported to be greater than 14 mg/dL along with serum Parathyroid Hormone (PTH) levels often above 1000 pg/mL. When serum PTH levels are 10 times the upper limit of the normal, it is considered diagnostic of PC. Surgical en-bloc resection without capsular breach is the only definitive cure for PC. The present case report included two patients who presented with features of single parathyroid glandular enlargement, hypercalcaemia, its consequences and with normal ionised calcium, but relatively low levels of elevated serum PTH (<300 pg/mL). They were operated and identified postoperatively as having PC. This rare presentation of PC where the preoperative serum PTH values were lower than usually seen in carcinoma, should alert endocrinologists and surgeons that lower levels of elevated serum PTH do not primarily exclude the possibility of carcinoma.