TSHR and pseudohypoparathyroidism type 1A: Resistance to TSH may occur in the context of several conditions affecting various elements of the TSH-signaling pathway: monoallelic or biallelic mutations in TSH receptor (TSHR) gene (38), and type 1a and 1c pseudohypoparathyroidism caused by loss-of-function variants in the GNAS1 gene, encoding for the α subunit of the Gs protein or, less frequently, in the PRKAR1A, PDE4D, or PDE3A genes (39, 40).