IL6 and obesity due to melanocortin 4 receptor deficiency: The aims of the study were to determine serum concentrations of selected adipokines (i.e., leptin, adiponectin, and chemerin), IL-6, and vitamin D in patients with a predominant histological type of thyroid malignancy—PTC, and to assess the associations between obesity, metabolic syndrome, examined adipokines, and tumor staging.