Causes of ovulatory dysfunction include Polycystic ovary syndrome Hyperprolactinemia Hypothyroidism Perimenarche or perimenopause Primary ovarian insufficiency Idiopathic (sometimes occurring when gonadotropin levels are normal) During perimenopause, AUB-O may be an early sign of ovarian insufficiency; follicles are still developing but, despite increasing levels of follicle-stimulating hormone (FSH), do not produce enough estrogen to trigger ovulation.