Variations in the genes TG, TPO, NIS, PDS, PAX8, NKX2-1, NKX2-5, IYD, FOXE1, JAG1, DOUX2, DOUXA2 and TSH-R are associated with congenital hypothyroidism and/or nodular goitre (14, 24, 25). Here, TPO is linked to congenital hypothyroidism.