SLC16A2, also known as monocarboxylate transporter 8 (MCT8), is responsible for the transport of thyroid hormone 3 (T3) into the nerve cells in the developing brain. After T3 is transported into a nerve cell, it interacts with intranuclear receptors, which activate or inhibit the expression of specific genes that are related to cell migration, dendrite formation, and synapse development. SLC16A2 is also distributed in several organs such as the liver, heart, brain, thymus, intestine, ovary, prostate, pancreas, and placenta. A mutation in the SLC16A2 gene inhibits the transport of T3 into the brain and results in the Allan-Herndon-Dudley syndrome, which is characterized by severe intellectual disability and impaired movement.