Blunted hormonal response to exercise in fibromyalgia patients : a clue to its pathogenesis

Abstract EN

Objective: Prolactin and arginine vasopressin response to exercise were studied in 16 fibromyalgia patients and 10 normal controls in order to clarify the effect of exercise as a stress factor on the hypothalamic pituitary axis in those patients.

Procedure: Plasma AVP was measured with RIA while serum prolactin was measured withy ELISA.

Morning samples for both hormones were withdrawn under basal conditions and after 15 minutes of cycling exercise.

Results: Statistical analysis with student t- test revealed non-significant difference between patients and controls in either basal or post-exercise hormonal level for both hormones denoting that basal hormonal levels for both hormones are not different.

Comparing pre- and post-exercise hormonal levels, there was a highly significant increase in AVP (p < 0.0001) and prolactin (p < 0.05) after exercise (paired t- test) as compared to the basal pre-exercise level in the control group, a normal physiological response to exercise that was previously reported by some authors.

On the other hand fibromyalgia patients had blunted hormonal response to exercise for both hormones with a statistically insignificant difference between pre- and post-exercise levels (p > 0.05).

Conclusion: These findings suggests that fatigue, which is one of the main manifestations of fibromyalgia patients, could be due to the disturbed neurohormonal response to exercise and that hypofunction of the HPA axis during stress may have a role in the pathogenesis of this disorder.

Further clarification of neuroendocrine axis function and relation of the HPA axis hormones and various manifestations of fibromyalgia and their relation to stress may lead to better understanding of the disease and improved therapeutic strategies.