Acta Clin Croat. 2010 Dec ; 49(4):421-7. Treatment of ovarian hyperstimulation syndrome: new insights. Kasum M, Oresković S. SourceUniversity Department of Obstetrics and Gynecology, Human Reproduction Unit, School of Medicine, University of Zagreb, Zagreb, Croatia. mkasum@gmail.com Abstract Ovarian hyperstimulation syndrome is the most serious iatrogenic complication resulting from ovarian stimulation. Currently there is no clear evidence of absolute efficacy for most of standard preventive and curative methods. Recent studies indicate that human chorionic gonadotropin increases vascular endothelial growth factor, vascular endothelial cadherin and vascular permeability via endothelial adherence junctions. Vascular endothelial growth factor plays a pivotal role in the pathophysiology of the condition and therefore vascular endothelial factor antagonism has been suggested for the prevention of the syndrome. Since vascular endothelial growth factor is also a physiological regulator of folliculogenesis, progesterone secretion and endometrial angiogenesis, its complete inactivation by specific blockers could produce undesirable effects interfering with early pregnancy development and therefore they cannot be used clinically. Recently, low doses of dopamine agonists (cabergoline) have been shown to counteract vascular endothelial growth factor induced vascular hyperpermeability, reducing the incidence of the syndrome by prophylactic treatment without compromising pregnancy outcome. The absence of undesirable side effects could make cabergoline an effective and safe etiologic approach for the prevention and treatment of the syndrome. A novel approach has suggested that metformin may also be helpful in the syndrome prevention in women with or without polycystic ovary disease.