Bone Abstracts

Background: Activating mutations in the calcium sensing receptor can result in severe hypoparathyroidism with symptomatic hypocalcaemia. Complications of treatment with calcitriol or alfacacidol include hypercalciuria, nephrocalcinosis and renal failure. The use of synthetic parathyroid hormone (PTH 1–34, teriparatide) provides a more physiological treatment option and reduces the risk of hypercalciuria.

We report our experience with such a patient who had increasing requirements of PTH on multiple daily injections over 5 years. The large PTH requirements significantly reduced when multiple s.c. injections were changed to a continuous subcutaneous infusion of PTH (CSIP).

Presenting problem: A 1-year-old girl presented with hypocalcaemic convulsions and was found to have hypoparathyroidism due to an activating mutation of the calcium sensing receptor (CaSR) (c.2528C>A p.A843E) which prevents secretion of PTH under any circumstances. She was initially treated with alfacalcidol but continued to have episodes of symptomatic hypocalcaemia, particularly associated with intercurrent infections. After lengthy informed discussion with the parents, she was treated with daily injections of teriparatide. Normocalcaemia was initially maintained with twice daily injections but, after 3 years of treatment, her dose increased to 75 μg daily in three divided injections, almost twice the recommended adult dose. In order to try to reduce the total dose of PTH and the need for multiple daily injections, she was changed to CSIP using an insulin infusion pump to deliver the PTH at a constant rate throughout the day and night.

Clinical management: Plasma calcium was 2.2 mmol/l prior to starting treatment. PTH 1–34 was infused initially at a rate of 72 μg/day (equivalent to the dose being received by injection) but she rapidly became hypercalcaemic. 72 h after starting the infusion, her total dose had been reduced by 50% and her calcium stabilised.

Discussion: Shortly after starting treatment with a continuous infusion of PTH, the total dose was able to be reduced significantly indicating that the PTH was much more effective when given in his manner. She no longer required multiple injections and only needed to have her giving set changed every 3 days. We recommend that this is the treatment of choice in such circumstances.