PRL and hyperprolactinemia: Prolactin levels were markedly elevated in some patients with tumors, causing minimal distortion of the pituitary stalk; conversely, prolactin levels were often normal despite evidence of massive stalk distortion.(20) A recent study involving 107 patients with NFPAs demonstrated that the presence of a cystic or hemorrhagic tumor and the presence of pituitary stalk deviation were statistically more frequent in patients with hyperprolactinemia.