Dysregulated bile acid metabolism can influence systemic inflammation, neuroendocrine signaling, and brain function via the farnesoid X receptor (FXR) and TGR5 receptors, providing a plausible mechanistic link between gut dysbiosis and the neurocognitive symptoms (“brain fog”) of ME/CFS. This evidence concerns the gene NR1H4 and myalgic encephalomeyelitis/chronic fatigue syndrome.