PRL is unique among the pituitary hormones in that the predom- inant central control mechanism is inhibitory, reflecting tonic dopa- mine-mediated suppression of PRL release. This regulatory pathway accounts for the spontaneous PRL hypersecretion that occurs with pituitary stalk section, often a consequence of head trauma or com- pressive mass lesions at the skull base. Pituitary dopamine type 2 (D 2 ) receptors mediate inhibition of PRL synthesis and secretion.