MCT8 deficiency, also known as Allan–Herndon–Dudley syndrome, is an X-linked recessive disorder that presents with intellectual disability, motor retardation, spastic quadriplegia, and hypotonia from infancy due to the impaired uptake of 3,3’,5-triiodothyronine (T3) into neurons2–5 The prevalence of MCT8 deficiency is unknown. Here, SLC16A2 is linked to Intellectual disability.