RETN and obesity due to melanocortin 4 receptor deficiency: The adipocyte-derived substances participating in the regulation of the metabolism of adipose tissue and therefore determining the occurrence of obesity include, among others: adipokines and hormones (leptin, resistin, adiponectin, estrogens), cytokines (interleukins 1, 6, 8, 10 etc.), other substances, e.g., enzymes (cholesterol ester transfer protein, lipoprotein lipase), and many more [53].