Activin plays an important role in numerous physiological processes such as cell differentiation and remodeling, regeneration and repair of tissues from various organs, angiogenesis, morphogenesis of glandular organs, pluripotency and differentiation of stem cells, cell adhesion and apoptosis. It participates in reproductive processes like embryogenesis, in the expression of Follicle Stimulating Hormone and Luteinizing Hormone and maturation of ovarian follicles and therefore has application in the area of reproduction of vertebrates. Given the economic importance of activin, we develop an efficient and economical method for the production of recombinant human activin A (rACT), using as expression system the yeast Pichia pastoris. rACT showed biological activity as it induced, on submicromolar dose, the increase of ovarian mass and the ovulation process in a mammal model.