Therefore, the aims of this study are: (i) to determine the levels of PAI-1 protein in the pediatric age which will allow for the definition of a normal range which can be a useful tool for correctly estimating the presence of alterations of hemostasis; (ii) the correlation, if it exists, of BMI with VD levels in patients with obesity; and (iii) the study of some cardiovascular risk indicators and the possible correlation with both PAI-1 and VD levels. This evidence concerns the gene SERPINE1 and obesity due to melanocortin 4 receptor deficiency.