Plasma levels on nociceptin in female fibromyalgia syndrome patients.

Fibromyalgia syndrome (FMS) is a frequent pain disorder in women. The pathophysiologic mechanism behind this disorder is still unexplained; however, alterations in both monoamines, neuropeptides and in the stress axis have been found. This study was designed to determine the levels of the newly discovered neuropeptide nociceptin in hormonally different FMS patients and corresponding controls. The results showed that the nociceptin concentrations of the patients were lower than in controls. It also showed decreased levels with significant differences between the cyclic patients in the luteal phase of the menstrual cycle, compared to the corresponding controls. Our results suggest that the perturbed nociceptin concentrations of the FMS patients may be linked to both the sex hormones and to the stress system and that these changes might be one of several possible pathophysiologic mechanisms involved in the FMS.