NKX2-1 and thanatophoric dysplasia: TD, which is caused by abnormal development of the thyroid gland, has been reported to be associated with mutations in the following genes: thyroid-stimulating hormone receptor (TSHR), NK2 homeobox 1 (NKX2-1), NK2 homeobox 5 (NKX2-5), forkhead box E1 (FOXE1), paired box 8 (PAX8), and GLIS family zinc finger 3 (GLIS3) (3).