Endocrine Abstracts

Case history: A 62-year-old male presented with generalised weakness, decreased oral intake, increased lethargy and polydipsia. He had a background of type 2 diabetes, hypercholesterolemia, and was a heavy smoker. No family history of parathyroid disease, other disorders causing hypercalcaemia or other endocrine tumours.

Investigations: Initial blood results showed severe hypercalcaemia adjusted calcium 3.87mmol/l (2.2 - 2.55mmol/l), significantly raised PTH 61.8pmol/l (1.6 - 6.9pmol/l), normal serum phosphate, normal renal function with vitamin D of 77nmol/l He had not reported previous fractures or history of renal calculi. Localisation studies with neck ultrasound did not localise a parathyroid adenoma but showed a left thyroid spongiform nodule (U2). Subsequent Technetium99m (99mTc)-sestaMIBI-99 scan demonstrated a functional parathyroid adenoma in the upper left part of the thyroid.

Results and treatment: Due to multiple episodes of severe hypercalcaemia, he required frequent hospital admissions for intravenous fluids and intravenous bisphosphonates. He was temporarily started on Cinacalcet which was uptitrated to 90 mg four times daily to manage his hypercalcaemia whilst awaiting definitive management. Two months following his initial presentation he underwent parathyroid surgery, due to suspicion of carcinoma intra-operatively, he underwent a hemithyroidectomy. Histology report confirmed a 30 mm parathyroid carcinoma, GATA3 positive. Proliferation index indicated by MIB1 was less than 5% with no infiltration into the thyroid, or local lymph nodes. There was no evidence of metastasis on subsequent CT scan of chest, abdomen and pelvis. PTH and calcium normalised with no hypocalcaemia post operatively and resolution of initial presenting symptoms.

Conclusion: : Parathyroid carcinoma is an extremely rare disease accounting for less than 1% of primary hyperparathyroidism. This case demonstrates the challenge of pre-operative diagnosis due to the difficulty in distinguishing from benign disease, owing to the absence of reliable diagnostic criteria and initial presentation can be similar. It is essential to consider the diagnosis of parathyroid carcinoma in cases of severe hypercalcaemia with marked rise in PTH (often over 5 times the upper limit of the normal range). Unlike benign causes of hyperparathyroidism, parathyroid carcinoma has an equal prevalence in males and females, with a lower average age of diagnosis and is more likely to have concomitant renal and skeletal involvement. Most cases are sporadic however rarely it can occur in those with familial hyperparathyroidism. Further elucidation of the molecular pathogenesis of parathyroid carcinomas will enhance our understanding of this rare entity