Endocrine Abstracts

A 60-year-old man presented with symptomatic primary hyperparathyroidism. At this time serum corrected calcium was 3.1 mmol/l (2.15–2.65 mmol/l) and after investigation bilateral parathyroid exploration was performed. A suspected adenoma was identified in the right inferior gland and removed. The remaining glands appeared normal. The adenoma was confirmed histologically. Early post-operative calcium was normal (2.48 mmol/l).

He remained well and calcium stayed within the normal range for 23 months. After this time serum corrected calcium started to rise to above the normal range with readings between 2.7 and 2.8 mmol/l. He remained asymptomatic. At 33 months calcium was 3.47 mmol/l with PTH of 231 pg/ml (15–70 pg/ml). A parathyroid subtraction scan did not identify an adenoma. A further bilateral neck exploration was performed. Intraoperatively what appeared to be a large left inferior parathyroid adenoma was identified and removed. Both superior parathyroid glands appeared normal. Histological examination of the removed tissue was in keeping with nodular/pseudoadenomatous hyperplasia rather than adenoma. Calcium settled post operatively to 2.39 mmol/l. MEN type 1 screening was negative.

Two possible explanations have been postulated for relatively early recurrence of hypercalcaemia after normalistaion of calcium by surgery. The first is temporary surgical damage which seems unlikely with the time course described here. The second is the rarely reported diverse functioning among multiple abnormal parathyroid glands whereby a large tumour may dominate as the main cause of hypercalcaemia and as a result suppress parathyroid secretion from another abnormal gland. We postulate that this occurred in the present case.