To the Editor: The thyroid and lungs develop as outgrowths of the ventral foregut. Differentiation and early function of both organs appear to be related through the common expression of the thyroid transcription factor-1 (TTF-1) gene on chromosome 14q13. In embryos, the pattern of expression of this gene is largely restricted to the epithelium of the developing thyroid and airways and the ventral forebrain.¹ Experimental evidence suggests that TTF-1 mediates thyroid-specific gene transcription and pulmonary production of surfactant proteins.²,³ We identified a heterozygous deletion of the TTF-1 gene in a newborn infant with thyroid dysfunction and respiratory . . .