ESPE Abstracts (2018) 89 P-P2-043

aAPHP, Department of Endocrinology and Diabetology for Children, Bicêtre Paris-Sud, Le Kremlin Bicêtre, France; bAPHP, Reference Center for Rare Disorders of Calcium Metabolism, Bicêtre Paris-Sud, Le Kremlin Bicêtre, France; cAPHP, Department of Genetics and Hormonology, Bicêtre Paris-Sud, Le Kremlin Bicêtre, France

Introduction: X-linked hypophosphatemic rickets (XLHR) is due to mutations in the PHEX gene inducing increased levels of fibroblast growth factor 23 (FGF23), phosphate wasting, hence rickets. FGF23 is suspected to be as an important metabolic regulator of glucose and lipid metabolism.

Objective: To describe the metabolic profile (body mass index, blood pressure, glucid and lipid profile) in patients with XLHR and evaluate the correlation between FGF23 levels and metabolic biomarkers.

Results: 53 XLH patients (17 boys and 36 girls)(PHEX mutated) were included (mean age: 8.0±4.3 years (range 0.3–18)). Each subject was classified based on International Obesity Taskforce (IOTF) cut off values of BMI for age and sex as overweight (IOTF >25) or obese (IOTF >30). Mean IOTF of study population was 23.9±3.2. 42% of patients had IOTF > 25 of which 12/53 (22%) were overweight (IOTF mean: 25.9±1.13) and 11/53 (20%) were obese (IOTF mean: 31.2±3). When stratified by age, children show a dramatic increase of BMI z-score (SDS) over time (at 2 years: 0.5±0.3, 5 years: 0.9±0.3, 10 years: 1.1±0.4 and 15 years: 1.4±0.5). None of the patients had hypertension. Four patients out of 53 had hyperglycemia, i.e. fasting blood sugar >1.1 g/dl; seven patients had HDLc <1.03 mmol/l, 7 had low HDL cholesterol and 11 had high LDL cholesterol level (> 1.24 mmol/l) which correlated with FGF23 level (P=0.0237).

Conclusion: This pilot study shows that children with XLHR gain too much weight during childhood, and that there may be an association between FGF23 and the development of metabolic syndrome. Further investigations are needed in a larger cohort of children and in adults to define the specific roles of FGF23 and PHEX in the development of metabolic syndrome.

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