Immunoreactive ACTH, beta-endorphin, and cortisol levels in plasma following spinal manipulative therapy

This study examines the possibility of a humorally mediated analgesic response to spinal manipulative therapy by determination of plasma levels of beta-endorphin, adrenocorticotropic hormone (ACTH), and cortisol before and after intervention. Forty male subjects (20 symptomatic, 20 asymptomatic) were allocated into four equal groups. Two treatment groups were given spinal manipulative therapy, and two groups underwent a sham procedure. Blood samples were taken via indwelling butterfly needles pre- and postintervention in all four groups, and levels of immunoreactive ACTH, immunoreactive beta-endorphin, and cortisol determined by radioimmunoassay. No differences in ACTH or beta-endorphin were found between sham and treated groups, or between pre- and postintervention in any group; cortisol levels fell over the course of the study in all groups. The findings thus appear to exclude a humoral role for beta-endorphin in mediating the analgesic response to spinal manipulative therapy; in addition, they suggest that such therapy is not a stressor that activates the hypothalamo-pituitary-adrenal axis.