Hyperprolactinemia in hepatic encephalopathy may result from impaired central dopaminergic neurotransmission

Ten patients with liver disease and hepatic encephalopathy (HE) and eight normal controls were studied. Five of the 10 HE patients had hyperprolactinemia. The administration of L-dopa produced a decrease of serum prolactin in all. Prior administration of Carbidopa, a peripheral decarboxylase inhibitor, did not change the prolactin suppression by L-dopa in the normal controls or in the patients with normal baseline prolactin levels. In the hyperprolactinemic group, Carbidopa significantly inhibited the response to L-dopa. Impaired central neurotransmission, at least involving the hypothalamic-pituitary dopaminergic system, may underlie the hyperprolactinemia in HE.