Menin, a product of the MEN1 gene, is related to the ontogeny of several cancers such as MEN1 and sporadic endocrine tumors, although it is considered to be a tumor suppressor. Many proteins interact with menin, and it is involved in various biological functions in several tissues. Menin plays some physiological and pathological roles related to transforming growth factor-beta (TGF-β) signaling pathway in the parathyroid, and it is implicated in the tumorigenesis of parathyroid tumors. In bone, the bone phenotype was observed in some menin-deleted mice. Menin is considered to support BMP-2- and Runx2-induced differentiation of mesenchymal cells into osteoblasts by interacting with Smad1/5, Runx2, β-catenin and LEF-1, although it has different effects on osteoblasts at later differentiation stages through TGF-β-Smad3 and AP-1 pathways. Further research is expected to shed more light on the role of menin in bone.