A 64-year-old Caucasian woman presented with hypercalcaemia in 1994 with Parathormone (PTH) of 59.9 pmol/l and corrected Calcium of 2.68 mmol/l.
A parathyroid was removed and histology revealed carcinomatous change with vascular invasion suggesting probable dissemination. In November 1998 her corrected Calcium was 2.74 mmol/l with a PTH of 7.2 pmols/l but in 1999 the PTH ranged between 157 and 195 pmol/l with corrected Calcium above 2.80 mmol/l.
Extensive investigations including MIBI, octreotide and whole body FDG/PET scan showed no abnormal tracer distribution. In 2000 her PTH was 363 pmol/l and her corrected Calcium peaked at 3.35 mmol/l. A MIBI scan suggested a focus in the right pole of the thyroid but no parathyroid was found and a thyroid lobectomy was performed along with excision of the cervical thymus, which contained a histologically normal parathyroid. CT thorax in 2002 showed small multifocal metastases, which appeared stable in 2003 with no relapse in the mediastinum or at the primary site.
She received pamidronate infusions with no significant improvement in serum calcium and in 2003 she underwent stenting for hydronephrosis secondary to renal stone.
A repeat octreotide scan suggested a somatostatin positive tissue in the epigastric region and treatment with lanreotide was started. Her corrected Calcium remained above 3.27 mmol/l and in 2004 her PTH ranged between 320 and 487 pmol/l.
Cinacalcet, a new calcimimetic became available in 2004, but the licence was initially restricted to secondary hyperparathyroidism. Calcimimetics are agents that allosterically increase the sensitivity of the G-protein-coupled calcium-sensing receptor (CaSR) in the parathyroid gland to calcium. The CaSR is the principal factor regulating parathyroid PTH secretion and hyperplasia. Cinacalcet 30 mg was started in August 2004 and over the next three months her calcium normalised and PTH levels came down.