[Altered function of the hypothalamic-pituitary-adrenal axis in patients with acute, chronic and episodic pain]

Complex disorders of the hypothalamic-pituitary-adrenal axis constitute phenomena whose etiopathogenetic significance is the subject of controversy. The frequent coincidence with depressive symptoms further complicates interpretation.

Daily variations in cortisol levels were measured in 20 patients with acute pain, 27 with chronic pain in the lumbar musculoskeletal system, and 44 with episodic forms of headache to determine the daily average and then correlated with differentiated algesimetric data.

Patients with chronic and episodic pain had significantly higher scores on the McGill Pain Questionnaire and more affective items as an expression of depressive symptoms than patients with acute pain. The three groups did not however exhibit significant differences for the depression scale and list of "psychovegetative" disorders. In comparison to an age-matched pain-free control population (n=17), the average daily levels of cortisol were significantly higher in all three groups besides singularly elevated daily levels, but no correlations between the cortisol values and overall algesimetric data could be established. Chronic pain patients with high depression scores had significantly higher cortisol levels irrespective of pain intensity.

Pain experiences cause increased plasma cortisol levels with significant elevation of the daily average. Whereas in cases of acute pain, a direct but unspecific stress reaction not connected with the pain seems to be likely, the underlying cause in cases of chronic and episodic pain appears to be a complex and enduring activation of the hypothalamic-pituitary-adrenal axis, likewise independent from pain, probably associated with concomitant depressive symptoms and disruption of the circadian rhythm of release controlled by the hypothalamus.