Study of the Impact of Phosphate Supplementation on FGF23 Concentrations in Patients With Hypophosphatemia

NCT07827989 | Recruiting

• 1 other identifier: RBHP 2025 BOUVIER
• Study Type: interventional
• Target: 60
• Locations: 1 country
• Sites: 3

Brief Summary

Fibroblast growth factor 23 (FGF23) is the principal hormone regulating serum phosphate homeostasis. Secreted by osteocytes, it promotes renal phosphate excretion and suppresses the synthesis of 1,25-dihydroxyvitamin D. Measurement of FGF23 has become a key tool in the evaluation of hypophosphatemia, allowing distinction between FGF23-dependent forms (such as X-linked hypophosphatemic rickets, tumor-induced osteomalacia, and intravenous iron-induced hypophosphatemia) and FGF23-independent forms (including renal, gastrointestinal, nutritional, or drug-related causes). In healthy adults, several studies have demonstrated that FGF23 levels vary according to phosphate intake, decreasing during dietary restriction and increasing following phosphate loading. In hypophosphatemic conditions, however, available data are limited to X-linked hypophosphatemic rickets, where prolonged supplementation with phosphate and calcitriol leads to increased FGF23 levels, consistent with the underlying pathophysiology. Based on these observations, it is currently recommended, as a precaution, to measure FGF23 at least 15 days after discontinuation of phosphate supplementation in order to avoid transient elevations that may confound interpretation. In practice, however, this recommendation is difficult to implement, as most patients are already receiving phosphate supplementation at the time of evaluation. To date, no study has specifically assessed the effect of phosphate supplementation in patients with FGF23-independent hypophosphatemia, a condition characterized by appropriately low FGF23 levels. It therefore remains unclear whether supplementation could induce a transient rise in circulating FGF23, potentially leading to misclassification as FGF23-dependent hypophosphatemia (FGF23 \> 95 ng/L). This uncertainty provides a strong rationale for conducting the present study.

Conditions

Calcium-phosphorus Metabolism

Outcome Measures

Primary Outcomes (1)

• Impact of phosphate supplementation on plasma FGF23 levels in acquired FGF23-independent hypophosphatemia

  To determine whether phosphate supplementation modifies plasma FGF23 concentrations in patients with acquired FGF23-independent hypophosphatemia by studying changes in FGF23 concentrations following phosphate supplementation. The primary objective will be studied separately in two groups: first, in intensive care patients, and second, in oncology/rheumatology patients.

  Up to 21 days

Study Arms (1)

Patients hospitalized in adult intensive care, oncology, or rheumatology

OTHER

Biological: Blood sample

Interventions

Blood sample BIOLOGICAL

Collection of one EDTA tube for FGF23 measurement and one heparin tube for phosphorus measurement

Patients hospitalized in adult intensive care, oncology, or rheumatology

Eligibility Criteria

• Age: 18 Years+
• Sex: all
• Healthy Volunteers: No
• Age Groups: Adult (18-64), Older Adult (65+)

You may qualify if:

• Patients hospitalized in adult intensive care, oncology, or rheumatology
• Hypophosphatemia \< 0.8 mmol/L
• Clinical indication for phosphate supplementation

You may not qualify if:

• Chronic kidney disease, stage ≥ 3 (eGFR \< 60 mL/min/1.73 m²)
• Treatment with Ferinject® within the past year
• Sepsis
• Current treatment with active vitamin D
• Pregnancy or breastfeeding
• Inability to perform blood draws due to insufficient venous access
• Weight \< 35 kg (for intensive care patients only)
• Hypercalcemia \> 2.6 mmol/L

Sponsors & Collaborators

• University Hospital, Clermont-Ferrand: lead

Study Sites (3)

CHU Clermont-Ferrand Service de réanimation

Clermont-Ferrand, France

RECRUITING

CHU Clermont-Ferrand Service Oncologie

Clermont-Ferrand, France

RECRUITING

CHU Clermont-Ferrand Service Rhumatologie

Clermont-Ferrand, France

RECRUITING

MeSH Terms

Interventions

Blood Specimen Collection

Intervention Hierarchy (Ancestors)

Specimen Handling; Clinical Laboratory Techniques; Diagnostic Techniques and Procedures; Diagnosis; Punctures; Surgical Procedures, Operative; Investigative Techniques

Study Officials

• Damien BOUVIER

  CHU Clermont-Ferrand service de biochimie

  STUDY CHAIR

Central Study Contacts

Lise Laclautre

CONTACT

0473754963; promo_interne_drci@chu-clermontferrand.fr

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: NA
• Masking: NONE
• Purpose: OTHER
• Intervention Model: SINGLE GROUP
• Sponsor Type: OTHER
• Responsible Party: SPONSOR

Study Record Dates

• First Submitted: September 11, 2026
• First Posted: September 18, 2026
• Study Start: June 13, 2026
• Primary Completion (Estimated): May 1, 2027
• Study Completion (Estimated): September 1, 2027
• Last Updated: September 18, 2026

Record last verified: 2026-09

Data Sharing

• IPD Sharing: Will not share

Locations

FR (3)