Our result paralleled this hypothesis and showed that macroadenomas and sinus invasion were correlated with hyperprolactinemia in patients with prolactin-negative tumors compared to those with prolactin-positive tumors, implying that prolactin-negative adenomas could cause hyperprolactinemia through compressing the pituitary stalk and elevating intrasellar pressure. This evidence concerns the gene PRL and hyperprolactinemia.