Unanticipated remission of primary hyperparathyroidism following cinacalcet

Primary hyperparathyroidism (PHPT) is the most common etiology of hypercalcemia in an ambulatory setting and often arises from adenomatous growth of one (occasionally more than one) parathyroid gland. Patients with severe and symptomatic hypercalcemia, renal insufficiency, nephrolithiasis, osteoporosis, and younger than 50 are candidates for surgical removal of parathyroid adenoma(s). Medical treatment with a calcimimetic agent is offered to improve severe hypercalcemia when surgery is refused or considered unsafe. Here, we report a 68-year-old man with severe hypercalcemia due to PHPT and coronary artery disease who had to undergo percutaneous coronary intervention and stent placement. Surgery for PHPT was delayed for 6 months, and he received cinacalcet to lower serum calcium. He developed hypocalcemia 6 months later. After discontinuation of cinacalcet, his serum calcium remained normal. Ultrasonography of the anterior neck showed again a hypoechoic lesion posterior to the right thyroid lobe (presumed to be a parathyroid adenoma) but with smaller dimensions. This case highlights a rare but clinically significant phenomenon: the possibility of durable remission and anatomical regression of parathyroid adenoma following cinacalcet administration.