Evidence of reduced sympatho-adrenal and hypothalamic-pituitary activity during static muscular work in patients with fibromyalgia.

OBJECTIVE: To assess activation of the sympathetic nervous system and the hypothalamic-pituitary-adrenocortical axis during static exercise in patients with fibromyalgia.

PATIENTS AND METHODS: Sixteen patients with fibromyalgia and 16 healthy controls performed a static knee extension until exhaustion. Plasma catecholamines, adrenocorticotropic hormone and cortisol, as well as blood pressure and heart rate, were assessed before, during and following contraction. Plasma C reactive protein was analysed at baseline.

RESULTS: Blood pressure and heart rate increased during contraction (p < 0.001) and decreased following contraction (p < 0.001) in both groups alike. Compared with baseline, plasma catecholamines increased during contraction in both groups (p < 0.001), but patients with fibromyalgia had lower levels of plasma adrenaline (p < 0.04) and noradrenaline (p < 0.08) at all times. Adrenocorticotropic hormone increased at exhaustion in controls (p < 0.001), but not in patients with fibromyalgia, who also had lower adrenocorticotropic hormone at exhaustion (p < 0.02) compared with controls. There were no group differences, or changes over time in plasma cortisol. High sensitivity C reactive protein was higher in patients with fibromyalgia compared with controls (p < 0.02).

CONCLUSION: Patients with fibromyalgia exhibited a hypoactive sympatho-adrenal system as well as a hypo-reactive hypothalamic-pituitary axis during static exercise.