The third patient without any identified NKX2-1 mutations was a carrier of mitochondrial mutation; this raises the possibility of mitochondrial mutations contributing to thyroid dysgenesis.
Most permanent cases (80-85%) result from alterations in the formation of the thyroid gland during embryogenesis (thyroid dysgenesis), and several were shown recently to be produced by mutations in genes responsible for the development of thyroid follicular cells (TITF1, TITF2, PAX8 and TSHR).
In the present study we analyzed the thyroid transcription factor-1 (TTF-1) gene in patients with congenital hypothyroidism due to thyroid dysgenesis: three patients with athyrosis, five with ectopy, and one with hypoplasia.
Mutations in the gene encoding thyroid transcription factor-1 (TTF-1) are not a frequent cause of congenital hypothyroidism (CH) with thyroid dysgenesis.