1999; Royaux et al. 2000, 2001; Lacroix et al. 2001). Pendrin presumably acts as an HCO3−/Cl− exchanger in the inner ear, and mutations cause prelingual hearing loss with enlarged vestibular aqueducts (DFNB4) (Yang et al. 2005; Albert et al. 2006; Nakaya et al. 2007). In the thyroid, pendrin is essential for I− uptake, and defects in this protein may cause goiter and possibly hypothyroidism. Goiter combined with hearing loss is known as Pendred syndrome (Morgans and Trotter 1958; Reardon et al. 1999). The gene discussed is SLC26A4; the disease is Pendred syndrome.