Recombinant human parathyroid hormone (1-84) is effective in CASR-associated hypoparathyroidism

Gain-of-function mutations in the CASR gene cause Autosomal Dominant Hypocalcemia Type 1 (ADH1), the most common genetic cause of isolated hypoparathyroidism. Subjects have increased calcium sensitivity in the renal tubule, leading to increased urinary calcium excretion, nephrocalcinosis and nephrolithiasis when compared with other causes of hypoparathyroidism. The traditional approach to treatment includes activated vitamin D but this further increases urinary calcium excretion.

In this case series, we describe the use of recombinant human parathyroid hormone (rhPTH)1-84 to treat subjects with ADH1, with improved control of serum and urinary calcium levels.

We describe two children and one adult with ADH1 due to heterozygous CASR mutations who were treated with rhPTH(1-84). Case 1 was a 9.4-year-old female whose 24-h urinary calcium decreased from 7.5 to 3.9 mg/kg at 1 year. Calcitriol and calcium supplementation were discontinued after titration of rhPTH(1-84). Case 2 was a 9.5-year-old male whose 24-h urinary calcium decreased from 11.7 to 1.7 mg/kg at 1 year, and calcitriol was also discontinued. Case 3 was a 24-year-old female whose treatment was switched from multi-dose teriparatide to daily rhPTH(1-84). All three subjects achieved or maintained target serum levels of calcium and normal or improved urinary calcium levels with daily rhPTH(1-84) monotherapy.

We have described three subjects with ADH1 who were treated effectively with rhPTH(1-84). In all cases, hypercalciuria improved by comparison to treatment with conventional therapy consisting of calcium supplementation and calcitriol.