Recombinant human parathyroid hormone (1–84) replacement therapy in a child with hypoparathyroidism

First line conventional therapy of hypoparathyroidism comprises oral calcium and active vitamin D analogues. This approach may fail to correct hypocalcemia and hyperphosphatemia caused by the absence of parathyroid hormone and carries the risk of long-term complications including ectopic calcifications and renal damage. Full-length recombinant human parathyroid hormone (rhPTH[1–84]) is approved for the treatment of hypoparathyroidism in adults refractory to conventional therapy. To date, there is no data in children. Here, we report the successful use of rhPTH(1–84) in a 5-year old girl with hypoparathyroidism and concomitant chronic diarrhea manifesting as part of the autoimmune polyglandular syndrome type 1. Prior to starting rhPTH(1–84), the patient had been on conventional and later on rhPTH(1–34) continuous pump therapy. Conventional therapy failed to meet serum and urinary calcium target levels, whilst the pump therapy wasn't well tolerated and posed handling difficulties. Dose optimization for rhPTH(1–84) was informed by serum ionized calcium, spot urinary calcium-to-creatinine ratio and 24-hour urinary calcium excretion. Twice-daily subcutaneous injections of rhPTH(1–84) with a total dose of 3.35 μg/kg/d was well-tolerated, raised serum ionized calcium to target range (1.05–1.15 mmol/L) and normalized serum phosphate levels. Urinary calcium excretion was slightly above the recommended limit of 4 mg/kg/24 h, but improved compared to conventional therapy, with no evidence of nephrocalcinosis. Twice-daily administration stabilized serum calcium and phosphate levels compared to once-daily injections. rhPTH(1–84) treatment was well tolerated and the girl did not manifest any acute clinical complications of hypoparathyroidism throughout the entire observation period. Our experience with this case indicates that rhPTH(1–84) may be a physiological hormone replacement for managing hypoparathyroidism in children.