An observational study in Craniosynostoses, sponsored by Hospices Civils de Lyon. Recruiting at 1 site in France. Open to participants aged 4 Months to 18 Years. Per ClinicalTrials.gov, last updated 2026-04-16.
Sponsored by Hospices Civils de Lyon · Observational
FGF23 is the cornerstone of phosphate / calcium / vitamin D metabolism: it is synthesized mainly by osteocytes and acts as a phosphaturizing agent, inhibitor of dihydroxyvitamin D, and inhibitor of synthesis and secretion of PTH in most tissues.
The specific role of FGF23 on bone has yet to be demonstrated. In osteoblasts, overexpression of FGF23 in vitro suppresses not only osteoblastic differentiation but also the synthesis of the mineralized matrix independently of its systemic action on phosphate metabolism. In osteoblasts, FGF23 also regulates the secretion of osteopontin by directly suppressing transcription of alkaline phosphatase.
In some diseases such as hypophosphatemic rickets (HR), the direct role of FGF23 on bone has not yet been studied to our knowledge, whereas these genetic hypophosphatemias are secondary to overexpression of FGF23, whether an activating mutation of FGF23 or inhibitory mutations of its inhibitors (DMP1 and PHEX). However, patients with X-linked hypophosphatemic rickets (XLH) have higher circulating FGF23 levels than healthy controls and these levels are higher in treated patients.
Management of XLH consists primarily of correcting the native vitamin D defect by prescribing active vitamin D analogs as well as phosphate supplementation to improve bone mineralization and decrease dental complications, growth, and bone deformities. Recently, a new therapeutic option has been developed for XLH, burosumab, a human monoclonal antibody that binds and inhibits FGF23 activity. The use of burosumab is currently authorized in France in some pediatric patients with severe forms of XLH.
Independently of the indirect bone effects of phosphate correction and vitamin D levels, the direct role of burosumab on bone cells has never been studied. The objective of this project is to study the osteoblastic biology of patients with RH compared to control patients, and to evaluate the direct impact of the treatments used in this pathology on human osteoblasts.
51 studies on the registry are indexed under Craniosynostoses; 14 are open to participants now.
This study's planned enrollment of 20 is below the median of 43 across 26 observational studies indexed under Craniosynostoses.
Browse Craniosynostoses studies →Hospices Civils de Lyon is the lead sponsor of 1,866 studies on the registry; 448 are open to participants now.
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patients with craniosynostosis, idiopathic (control patients) or due to HR
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Anti-inflammatory medicines such as prednisone, prednisolone and dexamethasone — not the anabolic steroids used for muscle.
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Corticosteroids (steroids)
Anti-inflammatory medicines such as prednisone, prednisolone and dexamethasone — not the anabolic steroids used for muscle.
Studies differ in what they allow: check which steroid medicines, routes (tablets, injections, creams, inhalers, eye drops) and doses this study accepts.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Patients with idiopathic craniosynostosis
Biological: osteoblast biology study
Patients with craniosynostosis due to HR
Biological: osteoblast biology study
Describe the in-vitro action of burosumab and vitamin D on human osteoblastogenesis from osteoblasts from patients with craniosynostosis due to HR
Number of osteoblastic cells obtained at the end of differentiation
The analysis of osteoblastic differentiation obtained from the bone cells from patients with burosumab and/or 1-25 (OH) vitamin D (HR patients vs idiopathic craniosynostosis)
Time frame: Day 0
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