In the latter, due to inherited (autosomal dominant) REarranged during Transfection (RET) protooncogene alteration (9–12), MTC can be associated (multiple endocrine neoplasia type IIA and IIB – MEN IIA and MEN IIB) or not (familial medullary thyroid carcinoma – FMTC), with other endocrine neoplasia such as pheochromocytoma (PHEO) and/or hyperparathyroidism due to parathyroid hyperplasia or multiple adenomatosis (PTHAd) (13). This evidence concerns the gene RET and medullary thyroid gland carcinoma.