Plasma oxytocin levels in female fibromyalgia syndrome patients

Objectives: Fibromyalgia syndrome (FMS) is a chronic pain disorder, where 9 0% of the patients struck by the disorder are women. The neuropeptide oxyto cin is known to have antinociceptive and analgesic, as well as anxiolytic a nd antidepressant effects, which makes this neuropeptide of interest in fib romyalgia research. The aim of this study was to assess oxytocin concentrat ions in female FMS patients with different hormonal status and in depressed and non-depressed patients and relate oxytocin concentrations to adverse s ymptoms as pain, stress, depression, anxiety and to the positive item happi ness. Methods: Thirty-nine patients and 30 controls registered these symptoms dai ly during 28 days and blood samples for the assessment of oxytocin were dra wn twice in all patients and controls. Besides the daily ratings, depressio n was also estimated with the self-rating instrument Beck Depression Invent ory (BDI). Results: Depressed patients according to the BDI differed significantly wit h low levels of oxytocin compared to the non-depressed patients and the con trols. Low levels of oxytocin were also seen in high scoring pain, stress a nd depression patients according to the daily ratings; however, these subgr oups were small. A negative correlation was found between the scored sympto ms depression and anxiety and oxytocin concentration, and a positive correl ation between the item happiness and oxytocin. The oxytocin concentration d id not differ between the hormonally different subgroups of patients or con trols. Conclusion: The results suggest that the neuropeptide oxytocin may, togethe r with other neuropeptides and neurotransmitters, play a role in the integr ation of the stress axes, monoaminergic systems and the pain processing pep tides in the pathophysiologic mechanisms responsible for the symptoms in th e FMS.