CDCA8 and thyroid hypoplasia: Lastly, several single-gene mutations (in TSHR, NKX2.1, PAX8, FOXE1, GLIS3, NTN1, JAG1, CDCA8/BOREALIN, and TUBB1 (8–20)) cause CHTD, mainly orthotopic thyroid hypoplasia, most with associated syndromic features.