Chasing a parathyroid adenoma
M Banerjee1, AR Hearn2 & PA Vice1
This 65 years old lady, who had undergone neck explorations for parathyroid adenoma in 1972 and 2000, presented with vomiting, lethargy, muscle weakness and polyuria. On admission, her serum Calcium was 2.98 mmol/l (2.18-2.63) with elevated parathyroid hormone of 151 pg/ml (10-70). A Thallium-Technetium parathyroid scan was normal but Octreotide scan showed an area of uptake in the superior mediastinum. A MIBI scan followed, which was unhelpful as were ultrasound scan of the neck and MR scan of neck and mediastinum. Selective venous sampling showed a rise in the PTH level in the left superior mediastinum. During this period she received Pamidronate infusions at frequent intervals to keep her Serum calcium under control. She underwent her third neck exploration that was extended to her chest, when large amount of mediastinal fat was cleared, as there was no discernible tumour. No definite tumour could be identified from the excised tissue at histopathological examination. She has remained fine since her operation, as has her serum calcium. In her last clinic visit in November 2001, Serum calcium was 2.28 mmol/l and PTH 12 pg/ml.
The incidence of mediastinal parathyroid adenoma is rare but it is a known cause of surgical failure in treating hyperparathyroidism. In a large series of parathyroid adenoma resections, 19 similar cases were found out of a total 1035. Our case is similar to these and also exemplifies selective venous sampling being a valuable endocrine investigation tool, especially when most of the non-invasive tests have either been equivocal or negative.