Serum β-endorphin levels in chronic pelvic pain patients

β-Endorphin is a 31 amino acid opioid peptide with several physiologic roles of which analgesia is one. Numerous reports relate stress in humans to an increase in β-endorphin levels, suggesting a role for the peptide as a pain modulator. In chronic pain patients, elevated as well as reduced β-endorphin levels have been reported. The pharmacopathology, if any, of chronic pelvic pain remains unclear. This study is to investigate the levels of serum β-endorphin in chronic pelvic pain patients in relation to their perception of pain intensity. Twenty-three patients undergoing diagnostic laparoscopy for chronic pelvic pain were studied. Ten control patients were chosen from patients scheduled for elective laparoscopy sterilization who had no previous history of pelvic pain. Patients were asked to indicate their perception of pain intensity, using a visual analog scale, numbered one to ten. Laparoscopy was performed on all patients, with documentation of location, density of adhesions, and/or the presence of other pelvic pathology. All blood samples were drawn on the morning of surgery prior to laparoscopy. Results indicated a significantly (p<0.01) higher serum β-endorphin level in chronic pelvic pain patients compared to controls. The mean was 14.8pg/ml±13.2SD for pain patients and 4.3pg/ml±3.0SD for controls. There were significantly more pelvic adhesions (p<0.01) and pathologic abnormalities (p<0.001) upon laparoscopic examination in the study group than controls. Of particular interest is an inverse correlation between subjective pain levels and serum β-endorphin levels, i.e. the higher β-endorphin level, the lower the perception of pain. Our data suggest a role for β-endorphin in the modulation of chronic pelvic pain, i.e. of an opiate response to chronic pelvic pain. An elevation of β-endorphin level appears to decrease the patient's perception of chronic pain. This response, providing the body with its own natural analgesic, would be in agreement with the well-documented role of this peptide in relieving acute pain in patients.