Given that SOCS3 primarily inhibits signal transducer and activator of transcription (STAT) 3, it acts as a relatively specific inhibitor of STAT3 (16, 18). SOCS3 has been implicated in various autoimmune and inflammatory diseases, such as allergic diseases, inflammatory bowel disease, and obesity. Here, SOCS3 is linked to obesity due to melanocortin 4 receptor deficiency.