TH and migraine disorder: Todt et al. 2009 investigated a total of 53 SNPs in 10 genes from the dopaminergic system, including COMT, DBH, DDC, DRD1, DRD2, DRD3, DRD4, DRD5 SLC6A3 and TH, in a large German case-control cohort of migraine with aura and from this study the dopamine transporter SLC6A3 5p15 and DBH 9q34 enzyme emerged as significant [97].