[Estrogen receptors can regulate pain sensitivity. Possible explanation of certain chronic pain conditions]

Animal experiments as well as observations in humans have shown that somatosensory perception and pain sensitivity are influenced by gonadal hormones. These effects are likely to be exerted, at least in part, by the binding of estrogen to estrogen receptors present in neurons located in the superficial layers of the spinal dorsal horn. Neurons containing estrogen receptors in these locations have been found to express mRNA for the endogenous opioid enkephalin, and administration of estrogen has been shown to increase enkephalin transcription in the spinal cord. The possible clinical implications of these findings in relation to gender differences in pain sensitivity and chronic pain conditions are discussed.