GHRL and Prader-Willi syndrome: Three main research clusters of PWS could be summarized as (1) genetic mechanism: genomic imprinting, imprinting, UPD; (2) clinical aspects: obesity, hyperphagia, ghrelin, oxytocin, autism spectrum disorders, intellectual disability, hypothalamus; and (3) treatment options: GH deficiency, GH treatment (Figure 4a and b).