An Uncommon Case of Persistent Hypercalcaemia following Parathyroid Surgery

Primary hyperparathyroidism is present in approximately 1 in 500 people and occurs predominantly in post-menopausal women. The condition occurs in approximately 85% cases as adenoma, 14% cases as Parathyroid Hyperplasia and in 1% cases as Parathyroid Carcinoma (1) . Rarely it can occur as part of MEN (Multiple Endocrine Neoplasia) Type 1 and Type 2a and Familial Hyperparathyroidism. There is also often concomitant Vitamin D deficiency in Primary Hyperparathyroidism which needs to be replenished. Serum calcium is raised together with raised urinary calcium. Serum PTH should be >3pmol/l (N: 1.1-6.9 pmol/l). Approximately 20% patients will have PTH at the upper part of the normal range (2). Cinacalcet, a calcium sensing receptor agent, is now licensed for use in Primary Hyperparathyroidism. It decreases serum calcium but not urinary calcium. However the definitive treatment is in the form of Parathyroid surgery. Localization of abnormal Parathyroid glands with Ultrasound and 99m Tc-sestamibi scan is imperative before minimally invasive Parathyroidectomy. Parathyroid surgery is to be carried out by experienced Surgeons who carry out >20 operations per year and includes minimally invasive surgery for adenoma and Partial Parathyroidectomy in hyperplasia (2). The operation is successful in 95% cases. However in a small number of cases ectopic Parathyroid adenomas may be present and unless removed continue to cause persistent hypercalcaemia. A 67 year old woman was referred by her GP for raised serum calcium and raised Parathyroid hormone (PTH) to the clinic in June 2011. The patient had high calcium with raised PTH for six years, since 2005, prior to been seen in the clinic. The patient's renal function was normal and was diagnosed with Primary Hyperparathyroidism. Urinary calcium over 24 hours was mildly elevated and there was no evidence of kidneys stones on imaging. However a DEXA scan showed evidence of osteoporosis. The patient's Vitamin D level was normal and she was referred to a tertiary hospital for Parathyroidectomy. However the patient's serum calcium and PTH levels continued to remain high despite Parathyroid surgery. Subsequently for failed Parathyroidectomy the patient underwent a CT scan of thorax which suggested the presence of an ectopic mediastinal Parathyroid adenoma. The patient was not thought to be suitable for thoracic surgery and hence kept under monitoring for her serum calcium. The patient's recent Vitamin D level was found to be low and was commenced on Vitamin D supplementation. The calcium level became quite high and Vitamin D supplementation had to be withheld briefly. The decision was taken to treat the patient later with low dose Vitamin D simultaneously with Cinacalcet.