TPH1 and Stroke: Moreover, the T/C-C/A combined genotypes c.975-7T > C– KAT2 (rs1480544) and c.803+221C > A – TPH1 (rs1800532) caused a more than 20-fold reduction of the stroke risk in the Polish population (p = 0.001), whereas the C/C-C/C genotype increased this risk about ten times (p = 0.001).