A form of multiple endocrine neoplasia characterized by the presence of medullary carcinoma (carcinoma, medullary) of the THYROID GLAND, and usually with the co-occurrence of pheochromocytoma, producing calcitonin and ADRENALINE, respectively. Less frequently, it can occur with hyperplasia or adenoma of the parathyroid glands. This disease is due to gain-of-function mutations of the MEN2 gene on CHROMOSOME 10 (Locus: 10q11.2), also known as the RET proto-oncogene that encodes a RECEPTOR PROTEIN-tyrosine KINASE. It is an autosomal dominant inherited disease.