 In this study, it was found that approximately one-quarter of patients with apparent idiopathic hyperprolactinemia have macroprolactinemia. These results suggest that routine screening for macroprolactin should be performed on all patients with idiopathic hyperprolactinemia, regardless of their clinical features, in order to avoid misdiagnosis and unnecessary treatment with dopamine agonists. This article was authored by Lucio Villar, Clarisse Villar, Jose Luciano Albuquerque, and others.