Endocrine Abstracts

We report the case of a 63-year-old lady with refractory hypocalcaemia due to surgical hypoparathyroidism, decompensated by malabsorption following gastric bypass, successfully treated with recombinant human parathyroid hormone 1-84 (rhPTH), Natpar. She initially presented with medullary thyroid cancer aged 33 and was found to have MEN2A. She underwent thyroidectomy and developed post-surgical hypoparathyroidism. She was managed for over 20 years with alfacalcidol and oral calcium supplementation. In 2015, aged 57, she underwent Roux-en-Y gastric bypass surgery. Following this, she developed malabsorption and persistent, severe symptomatic hypocalcaemia (<1.5mmol/l). She struggled to tolerate oral calcium supplements finding calcium carbonate effervescent the most tolerable. She required long duration IV calcium infusions 3 times per week, in hospital, to maintain a calcium level >1.9mmol/l, which resulted in a negative impact on her quality of life. In 2018, Teriparatide was trialled (off-licence) but failed to maintain adequate calcium levels and the patient continued to require multiple calcium infusions per week. Additionally, she subsequently developed a portacath infection, which was removed and PICC line inserted. In 2021, she commenced Natpar 50 mg/day alongside IM ergocalciferol 300,000 units every 3 months. Within 4 weeks of treatment, her IV calcium dose was reduced and over subsequent weeks, the frequency of infusions was also reduced. After increasing Natpar to 75 mg/day, she no longer required IV calcium, maintaining calcium levels >2.0mmol/l with only transient symptoms of hypocalcaemia. She is now maintained on the maximum dose (100 mg/day) and remains on IM ergocalciferol, with plans to gradually reduce the alfacalcidol dose if serum calcium remains stable. This case demonstrates the challenges of managing hypoparathyroidism following gastric bypass surgery. Of note, chronic hypoparathyroidism is currently not a contraindication to Roux-en-Y gastric bypass. It also demonstrates the benefits of rhPTH replacement over conventional therapy in complex patients with chronic hypoparathyroidism and malabsorption.