Activins are a group of proteins that play a crucial role in various biological processes, including cell growth, differentiation, and reproduction. They belong to the transforming growth factor-beta (TGF-β) superfamily and are involved in regulating functions such as inflammation, metabolism, and tissue repair. Activins are produced in many tissues and can influence the behavior of different cell types. These proteins exert their effects by binding to specific receptors on the surface of target cells, initiating a signaling cascade that alters gene expression. Activins are particularly important in the reproductive system, where they help regulate follicle-stimulating hormone (FSH) production and influence ovarian and testicular functions.