SAT-259 Natural History of Anthropometric Parametres of Obesity in Children Affected by X-Linked Hypophosphatemia: Longitudinal Obserbational Study

Growing body of scientific evidence points to link between fibroblast growth factor-23 (FGF-23) and unfavourable metabolic profile (obesity, insulin resistance, hyperglycemia) and all-cause mortality in general population with normal kidney function. On the other hand, there is little information about metabolic profile in situations characterized by pathophysiologically high FGF-23 such as chronic kidney disease and X-linked hypophosphatemia (XLH). The aim of the present longitudinal observational study was to investigate anthropometric parameters of obesity and metabolic profile on large cohort of children with XLH. Methods: Among 263 XLH-patients registered in our centre we selected 168 children of 5-20 years (108 girls/60 boys). Total period of FU was divided in five sub-periods according age (group 0: birth, N=168; group 1: 5-7 years, N=122; group 2: 7-10 years, N=86; group 3: 10-15 years, N=89; group 4: 15-20 years, N=49). Anthropometric parameters (weight, height, BMI) were collected from birth (group 0) and for every point of FU (group 1-4). In each group, subjects were classified based on International Obesity Taskforce (IOTF) cut off values of BMI for age and sex as overweight or obese (IOTF 25-30 or ≥30 kg/m2, respectively). Metabolic parameters (total cholesterol, triglycerides, HDL, LDL, fasting glycemia and insulinemia, HOMA-IR) were measured at one point of FU in some patients (N=40). Results: In each group of FU (1,2,3,4) almost 1/3 of patients were classified as overweight or obese (29.5% vs 29.4% vs 28.1% vs 36.7%, respectively). Even without reaching statistical significance (p=0.75), there was a tendency of higher number of overweight or obese patients in group 4 (15-20 years) (36.7%) compared to group 1,2,3, which was explained by gender differences (higher number of overweight or obese girls compared to boys (42.4% vs 25%, respectively, p=0.35). There were no differences in BMI z-score (SDS) and BMI-IOTF between groups 1,2,3,4 during FU (BMI-SDS: 0.9±1.1 vs 0.7±1.0 vs 0.6±1.1 vs 0.6±0.9, respectively, p=0.45; BMI-IOTF: 23.5±4.4 vs 23.5±4.1 vs 23.7±4.2 vs 24.3±3.6, respectively, p=0.72). As regard other metabolic parameters, only 1 patient was diagnosed with diabetes mellitus at age 10. No other alterations were found. In each group of FU, no correlation was found between FGF-23 and BMI, total cholesterol, triglycerides, HDL, LDL, fasting glycemia, insulinemia, HOMA-IR. In conclusion, 1/3 of XLH children have phenotypically unfavourable metabolic profile expressed as overweight or obesity which is higher compared to general paediatric population. This phenomenon has increasing tendency after puberty, especially in girls, and requires strict follow-up of BMI in XLH patients. In order to understand the further development of metabolic parameters, the studies on adult XLH population are needed.