Menin is a tumor suppressor protein, encoded by the MEN1 gene, whose mutation can generate neoplastic disease in multiple tissues of the human body, which for generations can manifest as familial syndromes. The mutation generates a spectrum of diseases ranging from familial isolated hyperparathyroidism to multiple endocrine neoplasia type 1, characterized by neoplasm of parathyroid glands, anterior pituitary, endocrine pancreas and duodenum, among others. We present two cases of patients with endocrine neoplastic disease secondary to menin’s mutation. We review current information regarding its ethiopathogeny and its mechanism of carcinogenesis just recently understood. Additionally we review other mutations involved in the neoplastic syndromes exposed and present some final recommendations.