The value of prolactin in predicting prolactinοma in hyperprolactinaemic polycystic ovarian syndrome

Background: To identify a serum prolactin (PRL) cut-off value indicative of a PRL-producing adenoma in women with polycystic ovarian syndrome (PCOS) and hyperprolactinaemia and characterize such patients. Materials and methods: In the present retrospective case–control study, the medical records of 528 PCOS women were reviewed. Pituitary magnetic resonance imaging (MRI) was performed in PCOS patients with PRL levels ≥94.0 ng/mL and/or symptoms suspicious of a pituitary adenoma (PA). Prolactinoma diagnosis was made in the presence of an MRI-identifiable PA with biochemical and radiological response to dopamine agonists. Receiver operating characteristic (ROC) curve analysis was performed to determine a serum PRL threshold that could identify hyperprolactinaemic PCOS subjects with prolactinomas. Clinical, metabolic and endocrine parameters were also analysed. Results: Among 528 patients with PCOS, 60 (11.4%) had elevated PRL levels. Of 44 (73.3%) patients who had pituitary imaging, 19 had PAs, 18 normal MRI and 7 other abnormalities. Patients harbouring prolactinomas had significantly higher PRL levels compared to patients without adenomas (median PRL 95.4 vs 49.2 ng/mL, P <.0001). A PRL threshold of 85.2 ng/mL could distinguish patients with prolactinomas with 77% sensitivity and 100% specificity [Area Under the curve (AUC) (95%) 0.91(0.8-1.018), P =.0001]. PCOS women with prolactinomas were younger and had lower LH levels compared to women without prolactinomas. Conclusions: In women with PCOS, PRL levels exceeding 85.2 ng/mL are highly suggestive of a prolactinoma warranting pituitary imaging. Pituitary MRI could also be considered in young PCOS patients with milder PRL elevation and low LH levels.