Hypothyroidism, Congenital, Nongoitrous, 8, is also known as chng8. An important gene associated with Hypothyroidism, Congenital, Nongoitrous, 8 is TBL1X (Transducin Beta Like 1 X-Linked). Affiliated tissues include thyroid and hypothalamus, and related phenotypes are decreased circulating free t4 concentration and macrocephaly