Abstract
Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a disabling health condition, characterized by post-exertional malaise and accompanied by symptoms such as fatigue, pain, brain fog, and orthostatic intolerance. Affecting about 1 in 200 people, ME/CFS has no validated treatments and very few insights into its pathophysiology. Case-control studies of ME/CFS, or the related condition, postviral fatigue syndrome, have consistently demonstrated that patients exhibit an abnormally large increase in prolactin following administration of buspirone, a drug which acts at serotonin and dopamine receptors. Less replicated evidence of abnormal prolactin response comes from studies which tested d-fenfluramine, exercise, and insulin-induced hypoglycemia. The implications of these findings are not yet clear, though potential explanations include alterations in neurotransmitter systems or sex hormone pathways. This review discusses what is known about prolactin response in ME/CFS, and suggests future research directions.