Endocrine Abstracts

Sclerotic bone lesions are a rare cause of hypocalcaemia. Calcium and vitamin D malabsorption are recognised complications of gastric bypass surgery. We describe the case of a 45 year-old woman with severe persistent symptomatic hypocalcaemia secondary to metastatic breast cancer, complicated by a previous Roux-en-Y gastric bypass, and the development of hypoparathyroidism. Her corrected calcium levels fell repeatedly and precipitously despite treatment with up to 8g/day oral calcium carbonate, and 6 mg/day alfacalcidol given orally and then intravenously. During her prolonged hospital admission, she required maintenance calcium gluconate infusions of up to 40g/day. Her initial chemotherapy regime of gemcitabine and carboplatin was changed due to concerns of carboplatin exacerbating hypocalcaemia. After weeks of maintenance calcium infusions, she continued on capecitabine. Radium-223, an alpha-particle emitting radionuclide and calcium mimetic, was considered but deemed unsuitable due to concurrent visceral metastases and pre-existing pancytopaenia. We believe that chemotherapy was the definitive management of her hypocalcaemia, controlling the sclerotic lesions and eventually allowing us to maintain normocalcaemia with oral agents. Takeaway points from this unusual case are the complexity of hypocalcaemia drivers and the difficulty in management. The likely causative factors were sclerotic metastases, malabsorption due to her gastric bypass, and hypoparathyroidism. Breast cancer bone metastases are mostly lytic or mixed lytic-sclerotic, with sclerosis often resulting from treatment. Even in cancers with predominantly sclerotic metastases, hypocalcaemia is rarely encountered. It is unlikely that hypoparathyroidism was unrelated to her coincident medical problems, but we were unable to determine its aetiology. Hypoparathyroidism presenting after bariatric surgery can be extremely challenging to manage. Our attempts to improve calcium absorption with calcium carbonate/calcium lactate were unsuccessful. Similarly, oral and intravenous activated vitamin D were insufficient to overcome the draw on serum calcium from bone metastases.