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Treatment of Children and Adults With X-Linked Hypophosphatemia With Calcitriol Alone: A Prospective, Open-Label
Deborah Mitchell1,2,3, Mackenzie Jordan1, Sarah Gehman1
1Endocrine Unit, Massachusetts General Hospital, Boston, MA 02114, USA.
Context:
Preclinical studies demonstrate that treatment with calcitriol attenuates skeletal complications in mice with X-linked hypophosphatemia (XLH).
Objective:
This work aimed to assess serum markers of mineral metabolism, nephrocalcinosis, skeletal microarchitecture, growth, and evidence of rickets following calcitriol monotherapy in children and adults with XLH.
Methods:
A 1-year, prospective, single-arm, open-label study was conducted comparing baseline and 12-month outcomes. Participants were recruited from outpatient endocrinology clinics in the United States. Data were collected in a research unit. Eligible participants were aged 4 years or older, not pregnant, with baseline 25-hydroxyvitamin D of 20 ng/mL or greater and normal serum calcium. Participants were treated with calcitriol, with dose based on serum and urinary calcium concentrations, for 1 year. The primary end points were change in serum phosphate and nephrocalcinosis (all participants) and rickets severity score (children). Secondary end points included changes in additional markers of mineral metabolism, skeletal microarchitecture parameters via high-resolution peripheral quantitative computed tomography (all participants), and height z-scores (children).
Results:
Serum phosphate did not change over 12 months of optimized calcitriol treatment. Rickets improved in 2 of 4 children with open epiphyses; height z-scores were unchanged. Nephrocalcinosis scores remained stable. Adults had increased cortical thickness at the radius diaphysis (P = .012). Serum alkaline phosphatase decreased in children (P = .021) and parathyroid hormone trended lower both in children (P = .065) and adults (P = .063). Four participants developed mild hypercalcemia and 2 developed hypercalciuria that resolved with calcitriol titration.
Conclusion:
Calcitriol monotherapy is safe and well-tolerated in XLH, with modest benefits on laboratory indices of mineral metabolism and rickets.
Insights
Calcitriol monotherapy in X-linked hypophosphatemia (XLH) showed no change in serum phosphate but improved rickets in children. The treatment was safe and well-tolerated, with modest benefits observed.
Area of Science:
- Endocrinology
- Mineral Metabolism
- Skeletal Biology
Background:
- X-linked hypophosphatemia (XLH) is a rare genetic disorder characterized by impaired phosphate reabsorption and impaired vitamin D metabolism.
- Preclinical studies suggest calcitriol may mitigate skeletal complications in XLH.
Purpose of the Study:
- To evaluate the efficacy and safety of calcitriol monotherapy in children and adults with XLH.
- To assess changes in serum markers of mineral metabolism, nephrocalcinosis, skeletal microarchitecture, growth, and rickets severity.
Main Methods:
- A 1-year prospective, single-arm, open-label study.
- Participants (≥ 4 years old) received optimized calcitriol dosage.
- Primary outcomes included serum phosphate, nephrocalcinosis, and rickets severity score (in children).
Main Results:
- Serum phosphate levels remained unchanged after 12 months of calcitriol treatment.
- Rickets improved in 2 of 4 pediatric participants; height z-scores were stable.
- Nephrocalcinosis scores were stable; adults showed increased cortical thickness. Mild hypercalcemia/hypercalciuria occurred but resolved with dose adjustment.
Conclusions:
- Calcitriol monotherapy is a safe and well-tolerated treatment for XLH.
- The treatment demonstrated modest benefits on laboratory markers of mineral metabolism and rickets severity.
- Further research may explore combination therapies for enhanced efficacy in XLH management.
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