Introduction
The difficulties in managing hypoparathyroidism in a bariatric surgery patient are often under-estimated. Oral treatment with calcium carbonate and calcitriol is relatively simple but if absorption is impaired due to gastric bypass (the duodenum and jejunum are preferential sites for calcium absorption) then alternative strategies are needed.
Case:
A 37-year-old female underwent total thyroidectomy for Graves’ disease in 2016 with subsequent hypothyroidism and hypoparathyroidism. After surgery she was maintained on calcitriol 0.25mcg daily and calcium carbonate 1200mg daily. In 2018 she underwent Roux-en-Y gastric bypass in the management of Stage 3 Obesity (weight 153kg, BMI 56.2kg/m2). Two years later her weight had fallen by 72kg (BMI 29.8kg/m2) and she started to develop daily symptoms of nausea and vomiting followed by lethargy and paraesthesia. She presented to our hospital with serum ionised calcium 0.93mmol/L (1.15-1.30), corrected calcium 1.97mmol/L (2.10-2.60). Treatment included oral and intravenous calcium in addition to calcitriol. On discharge ionised calcium was 1.12mmol/L. Over the following months, doses of calcitriol were slowly titrated from 0.25mcg daily to 1mcg TDS as well as calcium carbonate to 2400mg daily and cholecalciferol 5000IU per day. Despite this ionised calcium level was frequently approximately 1.00 mmol/l. Symptoms included continuing paraesthesia and demineralisation and fracture of her teeth. Normocalcaemia was only achieved after conversion of calcitriol from capsule formulation to liquid formulation at an equivalent dosage. Liquid calcitriol is difficult to obtain and expensive. Ionised calcium levels stabilised at 1.17mmol/L after 1 week of liquid calcitriol treatment.
Conclusion:
Absorption of calcium from the gut deteriorated as the patient lost more weight. This case highlights the importance of considering gastric bypass surgery carefully after parathyroidectomy especially given the difficulty in management of hypocalcaemia. Whilst escalation of doses of supplementation may be required, some patients in the literature have required reversal of their gastric bypass.