IYD and familial thyroid dyshormonogenesis: Otherwise, 10–15% of cases are caused by thyroid dyshormonogenesis, which is associated with mutations in thyroid oxidase 2 (DUOX2), dual-oxidase maturation factor 2 (DUOXA2), thyroglobulin (TG), thyroid peroxidase (TPO), solute carrier family 5 member 5 (SLC5A5), solute carrier family 26 member 4 (SLC26A4) and iodotyrosine deiodinase (IYD) (Nettore et al., 2013; Cherella and Wassner, 2017).