NKX2-1 and cyclic hematopoiesis: Thyroid dysgenesis (TD), one of the most common etiologies of CH, was reported to be linked with mutations in genes including thyroid-stimulating hormone receptor (TSHR), paired box gene 8 (PAX8), thyroid transcription factor 1 (TTF1/NKX2-1), thyroid transcription factor 2 (TTF2/FOXE1), and NK2 transcription factor-related locus 5 (NKX2-5) [4].