Study of the Inappropriate Secretion of FGF23 in Patients Followed in Hospital in a Context of Hypophosphatemia

Study Overview
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Brief Summary
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The discovery of FGF23, the missing link in the long researched and finally found phosphate metabolism, marked a turning point in the understanding and physiopathology of specific hypophosphatemia. By inhibiting the renal reabsorption of phosphate and the production of calcitriol, FGF23 behaves like a hypophosphatemia hormone. Hypersecretion of FGF23 can occur in the case of genetic abnormalities (X-linked hypophosphatemic vitamin-resistant rickets, recessive or dominant hypophosphatemic rickets, McCune-Albright syndrome ...) or acquired abnormalities (oncogenic osteomalacia). Oncogenic osteomalacia can be induced by hyperproduction of FGF23 by benign tumours of mesenchymal origin. But more recently, several cases of malignant tumours secreting FGF23 have also been described (prostate, colon, breast, ovarian and lung cancers, pulmonary carcinoma, etc.)

Detailed Description
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To date, even if the incidence of FGF23-secreting tumours seems rare, no precise bibliographical data is available in the scientific literature. Future studies will have to address this issue in order not to underestimate the frequency of this complication. In this context, investigators would like to study the incidence of inappropriate FGF23 increase from a collection of biological samples carried out on 500 patients treated at the Clermont-Ferrand University Hospital for hypophosphatemia.

Official Title
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Study of the Inappropriate Secretion of FGF23 in Patients Followed in Hospital in a Context of Hypophosphatemia

Conditions
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Hypophosphatemia Without Immediate Anteriority, Unexplained Hypophosphatemia

Intervention / Treatment
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* Behavioral: unexplained hypophoshatemia


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Major patient, male or female Taken care of at the Clermont-Ferrand University Hospital or the Jean Perrin Centre In a context of hypophosphatemia (< 0.80 mmol/L), without immediate anteriority and not occurring during hospitalisation In capacity to express informed consent to participate in research Affiliated to a social security system Exclusion Criteria: Previously diagnosed hypophosphatemia Hypophosphatemia during hospitalisation Haemodialysis patient Refusal to participate

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Unexplained hypophosphatemia<br>Collection of additional blood volume (approximately 10 mL) during blood tests provided as part of the usual medical care. | Behavioral: unexplained hypophoshatemia<br>* Collection of additional blood volume (approximately 10 mL) during blood tests provided as part of the usual medical care.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Evaluate the frequency of blood levels of FGF23 unsuitable for hypophosphatemia | Assessing the presence of a blood level of FGF23 considered unsuitable for hypophosphatemia | day 0 | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Investigate the relationship between blood levels of FGF23 and other biochemical parameters in hospital patients with hypophosphatemia.. | Description: Measure blood levels of FGF23 in absolute value and other biochemical parameters (phosphatemia, phosphaturia, PTH, vitamin D ...) | Day 1 | 
| Investigate the relationship between blood levels of FGF23 and other biochemical parameters in hospital patients with hypophosphatemia. | Measure blood levels of FGF23 in absolute value and other biochemical parameters (phosphatemia, phosphaturia, PTH, vitamin D ...). | day 1 | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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FGF-23, Unexplained hypophosphatemia, Phosphate metabolism, Physiopathology of hypophosphatemia