Cinacalcet is a calcimimetic agent licensed for the treatment of secondary hyperparathyroidism and parathyroid carcinoma. Multiple endocrine neoplasia type 1 (MEN1) patients may benefit considerably from cinacalcet. Affected patients have hyperplasia of multiple parathyroid glands, rather than a single resectable adenoma. Surgical cure requires removal of all parathyroid tissue, which is often unsuccessful, resulting in multiple neck explorations and hypoparathyroidism. Cinacalcet provides a medical alternative by lowering both calcium and parathyroid hormone levels.
We performed a retrospective case notes review of eight consecutive patients treated with cinacalcet for MEN1 associated hyperparathyroidism. The aims were to determine effectiveness, tolerability and doses required. The cohort consisted of three male and five female patients, aged 2038 at diagnosis of hyperparathyroidism. Two patients commenced cinacalcet as primary treatment and six had previous surgery; two had multiple operations. Six patients exhibited complications of hyperparathyroidism renal calculi (3 patients), renal dysfunction (4 patients) and reduced bone mineral density (5 patients).
Prior to treatment, serum calcium levels ranged from 2.46 to 2.91 mmol/l, mean 2.72 mmol/l (normal range 2.152.65 mmol/l) and PTH levels ranged 4.836.5 pmol/l, mean 16.8 pmol/l (normal range 1.36.8 pmol/l). All patients were commenced on 30 mg twice daily cinacalcet with titration of doses; 5 continued on this dose, 3 patients reduced their dose to 30 mg once daily. Significant reductions were observed in serum calcium and PTH measurements (paired t-test). Serum calcium reduced by a mean of 13.1% (P=0.004), range 024.2%, with all patients achieving normocalcaemia. Serum PTH levels decreased by a mean of 41.7% (P=0.032), range 17.867.9%. Treatment with cinacalcet continued in all patients, duration ranging from 10 to 35 months, with maintenance of control throughout. Cinacalcet was well tolerated by 6 patients; 1 experienced nausea and 1 experienced diarrhoea, all symptoms fully resolved on dose reduction. These results demonstrate that cinacalcet is a well tolerated and effective treatment for complex primary hyperparathyroidism.