Hereditary forms, including multiple endocrine neoplasia types 2A and 2B (MEN2A [MIM: 171400]; MEN2B [MIM: 162300]), in which MTC is associated with other endocrinopathies, are almost invariably associated with germ-line point mutations in RET. The membrane tyrosine kinase receptor encoded by this gene is activated by the binding of ligand—co-receptor complexes, which induces dimerization of RET proteins and autophosphorylation of intracellular tyrosine residues [7]. Here, RET is linked to multiple endocrine neoplasia type 2.