IRF4 and Obesity: The list of genes implicated in hair greying phenotype include loci previously linked with smoking status (KIF1A, RUNX1, IRF4, BRINP1, TEX41, GRID1), BMI/obesity (GRID1, TEX41, SEMA4D, TBC1D22A, RUNX1), bone mineral density (RUNX1, TBC1D22A, TEX41), cardiovascular diseases (FGF5, MROH2A, DPEP1, GRID1) and immunology (RUNX1, TBC1D22A, IRF4, TMEM132C, GRID1). Importantly, all the above mentioned factors (particularly smoking) were linked with hair greying syndrome in previous research and therefore the link between these genes and greying seems to be justified [16, 33–36].