PRL and Oligomenorrhea: However, it does not seem that this level of PRL elevation could be a causative factor for irregular cycles or amenorrhea in women with PCOS because amenorrhea/oligomenorrhea occurs at PRL levels of more than 50 μg/L, while PRL levels ranging from 25 to 50 μg/L do not usually cause notable changes in menstrual cycles, though they may decrease overall fertility [68,89].