Specific genetic forms of syndromic and nonsyndromic thyroid dysgenesis and TSH resistance may be associated with mutations in the NK2 homeobox 1 (NKX2–1, brain-lung-thyroid syndrome; OMIM No. 610978); Forkhead box E1 (FOXE-1, Bamforth-Lazarus syndrome; OMIM No. 241850), Paired box gene 8 (PAX8; OMIM No. 218700), NK2 homeobox 5 (NKX2–5; OMIM No. 225250), TSH receptor (TSHR; OMIM No. 275200); and Gs α (GNAS, pseudohypoparathyroidism type 1A; OMIM No. 103580) genes (133, 138) (Table 3). Here, NKX2-5 is linked to pseudohypoparathyroidism type 1A.