MC4R and obesity due to melanocortin 4 receptor deficiency: MC4R expression is also associated with risk of early-onset obesity, increased lean mass and bone mineral density, and enhanced linear growth.[6] Two previous meta-analyses confirmed that the rs17782313 SNP near the MC4R gene was associated with risk of obesity[4] and type-2 diabetes.[7] It has been well-documented that obesity is the leading risk factor for many cancers.