Endocrine Abstracts

Hypercalcaemia due to malignancy can be treated with intravenous (IV) bisphosphonates. However, not all should receive bisphosphonates. It is important to establish the hypercalcaemia’s causes to guide treatments. A 71-year-old female initially presented to GP with back pains, lumbar spine magnetic resonance imaging showed widespread abnormal bone marrow signal, suspicious of metastasis. Bloods found hypercalcaemia (3.23mmol/L), raised parathyroid hormone (14.7pmol/L) and low 25-OH vitamin D (32nmol/L). She was admitted via the Emergency Department, given IV fluids, bisphosphonates (pamidronate), and Vitamin D replacement; treated for hypercalcaemia secondary to malignancy of unknown primary and referred to the Endocrinology team. When her calcium levels improved, she was discharged with plans for calcium monitoring at the Ambulatory unit. Further investigations were also done to locate the primary. A week later, her calcium levels were again, raised. She was given further IV fluids and bisphosphonates. Despite good initial responses to treatments, including zoledronic acid, her calcium levels kept creeping back up a week later, necessitating weekly attendances to the unit. Due to the imaging findings, and primary hyperparathyroidism, atypical presentation of osteitis fibrosa cystica was initially suspected. Following further investigations, It was later discovered she had metastatic breast cancer, and parathyroid adenoma (the culprit for treatment resistance). The adenoma was eventually removed surgically and her calcium has improved since. Using bisphosphonates to decrease calcium levels could trigger parathyroid adenomas to release more parathyroid hormone, causing rebound hypercalcaemia. Surgical removal of adenoma is more useful. Denosumab could also be considered because it is can lower parathyroid hormone-induced bone turnover. Nevertheless, further studies are required because there are limited data available on the use of denosumab in resistant hypercalcaemia secondary to primary hyperparathyroidism. In summary, patients with possible or known malignancy with hypercalcaemia could also have concurrent primary hyperparathyroidism. Giving them bisphosphonates might not solve their problems.