Answers-3 Hyperprolactinaemia may be manifest by a milky discharge from the breasts. Causes include, prolactinoma, hypothyroidism (far increased TRH), Non-functional tumour with stalk compression and drugs in particular dopamine antagonists such as chlorpromazine, haloperidol and domperidone. Pregnancy is a particularly common cause of hyperprolactinaemia. Other drugs that are occasionally reported include SSRIs. PCOs is often associated with idiopathic hyperprolactinaemia.