In the group of all patients with PD, a statistically significant positive correlation was observed for adiponectin and Hoehn–Yahr scale (r = 0.408; p = 0.017), resistin and Hoehn–Yahr scale (r = 0.477; p = 0.004), and melatonin and Hoehn–Yahr scale (r = 0.478; p = 0.002). The gene discussed is RETN; the disease is Parkinson disease.