The role of SMTNL-1 affecting female reproductive ability, along with a regulating effect on the insulin-dependent glucose metabolism. Since infertility disorders are often paired with glucose homeostasis diseases, and it is a severe case affecting an ever-increasing number of fertile age women, we aimed to investigate SMTNL-1’s effect in in vitro human endometrial cell (HESC) model by supplementing the media of the applied cell culture model with a biologically effective peptide representing a sequence of the SMTNL-1 protein. We investigated the peptide’s effect in control and gestational diabetes environment, establishing in vitro differentiation model.