Endocrine Abstracts

Spontaneous resolution of primary hyperparathyroidism following infarction for parathyroid adenomas is rare with infarction on treatment with cinacalcet being even rarer. A 53 year old female who presented to primary care with malaise was found to have biochemical evidence of primary hyperparathyroidism with adjusted calcium 3.31 mmol/l and parathyroid hormone 28.8 pmol/l. Previous medical history was unremarkable. Following discussion with endocrinology, treatment with cinacalcet 30 mg od was commenced and 2 weeks later adjusted calcium was 2.84 mmol/l and parathyroid hormone 19.5 pmol/l. At endocrine review 1 month later she was asymptomatic with no abnormal physical signs. Surgical intervention was agreed as the appropriate form of management after parathyroid imaging (US/SPECT CT/MIBI scan). Imaging confirmed the presence of an adenoma inferior to the right lobe of thyroid. A plan to continue treatment with cinacalcet pending surgery was unfortunately impacted by the Covid-19 crisis. At review 4 months later she was found to have stopped cinacalcet for 3 months and adjusted calcium was 3.25 mmol/l and parathyroid hormone 26.5 pmol/l. Treatment with cinacalcet 30 mg od was re-started. One month later she experienced pain and swelling anteriorly on the right side of her neck and paraesthesia of her fingers. Investigations confirmed adjusted calcium 2.22 pmol/l and parathyroid hormone 2.6 pmol/l by which time she was asymptomatic. Repeat imaging could not identify the previous adenoma. Eight months later adjusted calcium and parathyroid hormone remained normal at 2.47 mmol/l and 6.8 pmol/l respectively. Whilst cinacalcet has been demonstrated to decrease the size of parathyroid adenomas and to cause aptosis of parathyroid cells there have only been two previous reports of resolution of hyperparathyroidism following infarction. Whether cinacalcet was causative is speculative. We also speculate whether infarction is more common and under recognised.