Endocrine Abstracts

Introduction: Hypoparathyroidism is typically managed with calcitriol/alfacalcidol. Close monitoring of serum calcium is required as under-treatment causes symptomatic hypocalcaemia while over-treatment will cause nephrocalcinosis. We report three cases who demonstrated resistance to treatment during an intercurrent illness, necessitating increase in medication doses and monitoring.

Case series: Case 1: Two-month-old boy with newly diagnosed hypoparathyroidism due to GCMB2 mutation normalised his calcium on standard treatment with alfacalcidol and calcium supplements. He however developed bronchiolitis during admission, resulting in precipitous drop in corrected calcium (1.53 mmol/l) and seizures, requiring intravenous calcium infusion and significant increase in medication to normalise serum calcium (alfacalcidol 400 ng/day to 1500 ng/day, and calcium supplements 12 mmol/day to 48 mmol/day). He eventually needed recombinant PTH to achieve calcium homeostasis.

Case 2: A male infant diagnosed with hypoparathyroidism at birth responded to standard treatment. At 2 months he presented with bronchiolitis and recurrent hypocalcaemic seizures, requiring increase in dose of alfacalcidol (400 ng/day to 1500 ng/day) and calcium supplementation. However, following resolution of illness, he required rapid reduction in dosage due to hypercalcaemia.

Case 3: A six-month-old boy with Sanjad-Sakati syndrome on standard treatment for hypoparathyroidism presented with symptomatic hypocalcaemia following viral gastritis. He required increase in dose of alfacalcidol upto 3000 ng/day to normalise serum calcium. He was however lost to follow-up and presented again at 2 years of age with symptomatic hypercalcaemia (cCa>3 mmol/l) and severe nephrocalcinosis. To normalise his serum calcium and prevent further progression of nephrocalcinosis, he was commenced on recombinant PTH.

Conclusion and implications for clinical practice: Intercurrent illness in infants with hypoparathyroidism can lead to marked resistance to standard treatment and symptomatic hypocalcaemia. The underlying pathophysiology remains unknown, but would seem to involve more than just intolerance to oral medication and feeds. During such periods, close monitoring of calcium levels is required, with quick escalation in medication doses, as well as reduction to baseline on recovery to prevent over-treatment. Parental education is recommended, with future research evaluating the possible role of ‘sick-day’ rules similar to adrenal insufficiency.