In line with these data, Altay U et al., 2013 [38], reported that leptin serum values were significantly associated with PD severity, indicated by the percentage of positive bleeding on probing (BOP) sites, while the results obtained by Li Z et al., 2018 [41], revealed a significant association between leptin and resistin with CRP and IL-6, via a Spearman’s analysis, thus indicating an association between obesity and PD. Here, RETN is linked to obesity due to melanocortin 4 receptor deficiency.