Pathogenic variants in this gene result in a clinical syndrome of severe intellectual and motor disability and increased serum T3 concentrations, leading to thyrotoxic symptoms in peripheral tissues, together known as MCT8 deficiency [also known as Allan-Herndon-Dudley Syndrome (AHDS); OMIM number 300523] (8, 9, 14). This evidence concerns the gene SLC16A2 and Allan-Herndon-Dudley syndrome.