After these extensive backcrossing’s, TPO-CRE-ER transgenic and BRAFV600E knock-in mice were intercrossed for two generations to obtain mice that carry the BRAFV600E mutation under control of the thyroidal Cre recombinase on a genetic background (that of the NOD.H2h4 strain_) that is susceptible to thyroiditis. This evidence concerns the gene TPO and thyroiditis.