Background
Adynamia in fibromyalgia (FM) may be an expression of a functional deficit of the hypothalamic-pituitary-adrenal axis and be associated with below-normal levels of urinary cortisol. Our aim was to demonstrate that urinary cortisol was lower in patients with FM than in healthy subjects.
Findings
We measured urinary cortisol levels for a sample of 47 women aged 29 to 64 years (mean age 53 years), diagnosed with FM 2-3 years previously, and compared the results with those for a control sample of 58 healthy women of a similar age. Samples of 24-hour urine were appropriately collected and levels of urinary cortisol were measured using the fluorescence polarization immunoassay method. The mean cortisol value for the women with FM was 65.40+/-27.10 microg/L, significantly lower than the mean cortisol level for the control group, at 90.83+/-38.17 microg/L (p < 0.001).
Conclusion
Our study confirms that women with FM have significantly lower urinary cortisol levels than healthy women.
Information on 24-hour urine cortisol levels does not constitute useful information in itself, but may be valuable when combined with other clinical tests normally performed to diagnose FM. Although a dysfunctional hypothalamic-pituitary-adrenal axis can lead to decreased sensitivity and resiliency in the stress system, it does not necessarily affect baseline cortisol levels, so 24-hour urinary cortisol levels alone cannot be used to evaluate FM. Urinary cortisol is a potentially useful biochemical marker in terms of evaluating adynamia in FM, along with insulin-like growth factor 1, substance P and the terminal telopeptides [20]. Nonetheless, studies based on larger samples are necessary in order to corroborate these conclusions.
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