PRL and hyperprolactinemia: The prevalence of hyperprolactinemia in patients with NFPAs varies from 25% to 65%, with a mean prolactin level of 39 ng/mL (usually <100ng/mL).(4,5) This increase in prolactin levels is justified by the mechanism known as the "stalk or disconnection effect" (Figure 1), a result of a diminishing dopaminergic inhibition of lactotrophs when the pituitary stalk is compressed by large sellar tumors(6) or affected by inflammatory/infectious conditions.(1)