Thyroid transcription factor 1 (TTF-1) is a transcription factor that binds and activates the promoter of thyroid specific genes such as thyroglobulin, thyropero, Xenopus/Amphibian,idase, and thyrotropin receptor. TTF-1 is crucial in the maintenance of the thyroid differentiation phenotype. TTF-1 plays a role in lung development and surfactant homeostasis. Defects in TTF-1 are the cause of benign hereditary chorea (BHC), a movement disorder. Defects in TTF-1 are also the cause of choreoathetosis, hypothyroidism, and neonatal respiratory distress.