BA then travels from the gut through the systemic circulation and reaches the brain, where it crosses the BBB via monocarboxylated transporters of the SCL16 family [208], including SLC16A3, SLC16A4 and SLC16A7 that were found to be differentially expressed in the blood or postmortem brain tissue of TD patients [64,66]. This evidence concerns the gene SLC16A3 and thanatophoric dysplasia.