Mentuccia et al [26] first identified a polymorphism of the DIO2 gene (Thr92Ala), and studies of Thr92Ala in the DIO2 gene were carried out in humans and mainly focused on its associations with diseases, such as Alzheimer’s disease [27] and Kashin-Beck disease [28]. Here, DIO2 is linked to early-onset autosomal dominant Alzheimer disease.