Background: The fibroblast growth factor 23 (FGF23) is the most important hormonal regulator of circulating phosphate levels. Apart from this essential role, it may also act as a 'hormone-like' factor involved in glucose and lipid metabolism. It is believed to have a potential role in the development of insulin resistance.
Aim: The aim of the study was to compare FGF23 levels between two groups of obese adolescents: insulin resistant and non-insulin resistant.
Patients: The study included 36 obese, insulin-resistant adolescents (21 boys and 15 girls) of pubertal age (mean age, 13.95 years; Tanner stage IV or V). The control group consisted of 21 obese peers with normal HOMA-IR values.
Methods: FGF23 levels were measured in a fasting blood sample by Human Intact FGF-23 ELISA Kit (Immunotopics Inc., San Clemente, CA, USA). A standard oral glucose tolerance test was performed, which assessed fasting and 120 min postload plasma glucose and serum insulin levels; the insulin resistance index HOMA-IR was calculated. The definition of insulin resistance was based on a HOMA-IR threshold set for adolescents (> or = 3.16).
Results: There was a significant inverse correlation between FGF23 levels and HOMA-IR (R = -0.26, p < 0.05) in the study group. FGF23 levels were also significantly lower in the study group (9.8 vs. 11.9 pg/mL, p = 0.026).
Conclusions: In adolescents with simple obesity and insulin resistance, FGF23 levels are lower compared with obese adolescents with normal HOMA-IR.