Calcium-phosphorus MetabolismPHOSPHO-23NCT07827989
Study of the Impact of Phosphate Supplementation on FGF23 Concentrations in Patients With Hypophosphatemia
A study testing Blood sample in people with Calcium-phosphorus Metabolism, run by University Hospital, Clermont-Ferrand at 3 sites in France.
Trial 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. Read more about this study
- Who is it for?
- Ages 18 years and older
- Conditions the study is for
- Calcium-phosphorus Metabolism
- What is being tested?
- Blood sample
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 60 participants
- Where
- 3 sitesFrance
- Study dates
- 13 Jun 2026to Sep 2027
- Phase
- Interventional
- Are there results?
- Not yet: the study is under way
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 years and older
- All sexes
- No healthy volunteers
- Adult, Older adult
Who may be able to join
- Patients hospitalized in adult intensive care, oncology, or rheumatology
- Hypophosphatemia < 0.8 mmol/L
- Clinical indication for phosphate supplementation
Who cannot join
- 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
Trial locations and contacts
3 sites in 1 country. Contact the study team or a site near you to ask about taking part.
France3 sites, 3 recruiting
- Recruiting
CHU Clermont-Ferrand Service de réanimation
Clermont-Ferrand
Lise Laclautre, 0473754963, promo_interne_drci@chu-clermontferrand.fr
Laurent RENARD-TRICHE
- Recruiting
CHU Clermont-Ferrand Service Oncologie
Clermont-Ferrand
Lise Laclautre, 0473754963, promo_interne_drci@chu-clermontferrand.fr
Aurore DOUGE
- Recruiting
CHU Clermont-Ferrand Service Rhumatologie
Clermont-Ferrand
Lise Laclautre, 0473754963, promo_interne_drci@chu-clermontferrand.fr
Marie PICKERING
About this study
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.
Read more
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
- Being tested
- Blood sample
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Blood sampleBiological
Collection of one EDTA tube for FGF23 measurement and one heparin tube for phosphorus measurement
| Study group | Role | What they receive |
|---|---|---|
| Patients hospitalized in adult intensive care, oncology, or rheumatology | Other | Not described Receives: Biological: Blood sample |
What is being measured
The primary outcome is the main question the study is designed to answer.
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.
Measured: Up to 21 days
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted18 Sep 2026
- Study start13 Jun 2026
- Primary completionMay 2027 (estimated)
- Study completionSep 2027 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Calcium-phosphorus MetabolismStudies of the same condition, open and under way.
- More trials run by University Hospital, Clermont-FerrandThe sponsor's other registered studies.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase N/A
- Primary purpose
- Other
- Allocation
- Not applicable
- Intervention model
- Single group
- Masking
- None (open label)
- Enrolment
- 60 participants (estimated)
Sponsor and investigators
- Lead sponsor
- University Hospital, Clermont-Ferrand
- Sponsor type
- University, hospital or other
- Responsible party
- Sponsor
- Investigators
- Damien BOUVIER, Study chair, CHU Clermont-Ferrand service de biochimie
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT07827989
- Sponsor's protocol ID
- RBHP 2025 BOUVIER
- Acronym
- PHOSPHO-23
- Status last verified
- Sep 2026
- First submitted
- 11 Sep 2026
- Last updated
- 18 Sep 2026
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- No
Study at a glance
From the registry record, last updated by the sponsor on 18 Sep 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Study of the Impact of Phosphate Supplementation on FGF23 Concentrations in Patients With Hypophosphatemia
- ClinicalTrials.gov ID
- NCT07827989
- Acronym / sponsor ID
- PHOSPHO-23 / RBHP 2025 BOUVIER
- Conditions
- Calcium-phosphorus Metabolism
- Study type
- Interventional
- Recruitment status
- Recruiting
- Enrolment
- 60 participants (estimated)
- Lead sponsor
- University Hospital, Clermont-FerrandUniversity, hospital or other
- Study start
- 13 Jun 2026 (actual)
- Primary completion
- May 2027 (estimated)
- Study completion
- Sep 2027 (estimated)
- First posted
- 18 Sep 2026 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
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.
Study design
- Primary purpose
- Other
- Allocation
- Not applicable
- Intervention model
- Single group
- Masking
- None (open label)
- Number of arms
- 1
| Arm | Type | Receives |
|---|---|---|
| Patients hospitalized in adult intensive care, oncology, or rheumatology | Other | Biological: Blood sample |
Who may qualify
- Ages
- 18 years and older
- Sex
- All
- Healthy volunteers
- Not accepted
- Age groups
- Adult, Older adult
Key inclusion criteria (3 listed)
- Patients hospitalized in adult intensive care, oncology, or rheumatology
- Hypophosphatemia < 0.8 mmol/L
- Clinical indication for phosphate supplementation
Key exclusion criteria (8 listed)
- 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
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| Blood sampleCollection of one EDTA tube for FGF23 measurement and one heparin tube for phosphorus measurement | Biological | Patients hospitalized in adult intensive care, oncology, or rheumatology |
Primary outcome
Impact of phosphate supplementation on plasma FGF23 levels in acquired FGF23-independent hypophosphatemia
Time frame: Up to 21 days
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.
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 18 Sep 2026.
- Individual participant dataSharing planned: No
Related trials for Calcium-phosphorus Metabolism
RecruitingPhase 1/2
A First-in-human Study of KK8123 in Adults With X-linked Hypophosphatemia
X-linked Hypophosphatemia
Not yet recruitingEarly Phase 1
Phosphate & Kidney Stones
Kidney Stones, Calcium Oxalate Kidney Stones
Active, not recruitingObservational study
Local and Systemic Inflammatory Bone Alterations Related to Dental Implant Survival.
Peri Implant Mucositis, Peri Implant Bone Loss
Active, not recruitingObservational study
X-linked Hypophosphatemia Disease Monitoring Program
X-linked Hypophosphatemia, Hypophosphatemic Rickets
Recruiting
Phosphorus-31 Spectroscopy in Phosphate Diabetes
Phosphate Diabetes, X-linked Hypophosphatemia
Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part.
Damien BOUVIER study chair
CHU Clermont-Ferrand service de biochimie
3 sites in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A study testing Blood sample in people with Calcium-phosphorus Metabolism, run by University Hospital, Clermont-Ferrand at 3 sites in France.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 3 inclusion and 8 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: looking for participants now, as of the sponsor's last update on 18 Sep 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 3 sites in France. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
Are results available for this study?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
Contact Lise Laclautre (0473754963, promo_interne_drci@chu-clermontferrand.fr), or a site near the patient. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Impact of phosphate supplementation on plasma FGF23 levels in acquired FGF23-independent hypophosphatemia (time frame: Up to 21 days). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 18 Sep 2026.