In the present study, we comparatively investigated blood FGF 23 levels in hypertensive and normotensive children, and reported that (1) children with primary hypertension had significantly higher levels of FGF 23 than controls; (2) FGF 23 levels in patients with abnormal cardiac geometry were markedly higher than those in patients with normal cardiac geometry; and (3) there were no significant differences in FGF 23 levels between non-obese and obese hypertensive children, between patients with stage 1 and stage 2 hypertension, or between patients with normal and high insulin levels. This evidence concerns the gene INS and essential hypertension.