As expected, hyperprolactinemia was more common in patients with GH/PRL positive tumors (54.5% vs. 20.9%, P = 0.011), and the median PRL level was significantly higher in the GH/PRL positive tumors than in the GH positive tumors [22.14 (12.36–91.90) vs. 10.50 (7.12–18.90), P = 0.001]. This evidence concerns the gene GH1 and hyperprolactinemia.