FTO and obesity due to melanocortin 4 receptor deficiency: Genome-wide association studies (GWAS) have found a link between genetic differences in single nucleotide polymorphisms (SNPs) and a higher risk of both T2DM and GDM in different groups of people, including polymorphisms at the transcription factor 7-like 2 gene (TCF7L2), adiponectin gene (ADIPOQ), and fat mass and obesity-associated gene (FTO).