Mutations in the genes for TSH receptor [4], NKX2-1 (thyroid transcription factor 1) [5], thyroid transcription factor 2 [6], and paired box transcription factor 8 (PAX8) [7] have been identified in some patients with various forms of thyroid dysgenesis. The gene discussed is NKX2-1; the disease is hypothyroidism, congenital, nongoitrous, 2.