For microprolactinomas, PRL is usually 100 to 200 μg/L, however, outliers exist; in the Brazilian Multicenter Study on Hyperprolactinaemia which included 444 patients with microprolactinoma, mean PRL was 165 μg/L but ranged from 32 to 525 μg/L [32]. This evidence concerns the gene PRL and hyperprolactinemia.