HNF1A and obesity due to melanocortin 4 receptor deficiency: Monogenic diabetes, a rare form of diabetes seen in young people (types 4 and 5), is associated with heterozygous mutations in some genes, such as PDX1 and HNF1A. Variants of PDX1 and HNF1A genes are also linked with an increased risk of obesity, T2DM, or hyperglycemia [60-62].