In a study published in JCI Insight, Nadia Schoenmakers and colleagues first describe homozygous truncating mutations in an anion transporter SLC26A7, in children with dyshormonogenic congenital hypothyroidism (CH).
CH, the commonest neonatal endocrine condition, results in neurodevelopmental retardation if diagnosis and treatment is delayed, prompting newborn screening for the disorder. Dyshormonogenic CH, due to defective thyroid hormone biosynthesis, usually involves defects in genes (transporters, enzymes, thyroglobulin) known to be essential for this pathway.
The study shows that SLC26A7 is highly expressed in human and mouse thyroid and that Slc26a7 null mice also exhibit goitrous CH, indicating the critical importance of this transporter for hormone biosynthesis in both species. However, although SLC26A7 is homologous to Pendrin (SLC26A4), an iodide transporter which is defective in Pendred syndrome (dyshormonogenic goitre and deafness), it does not transport iodide. The molecular mechanism whereby SLC26A7 mediates dyshormonogenesis remains to be elucidated.