Menstrual variation in experimental pain: correlation with gonadal hormones.

Background: The results of studies examining the response to experimental pain during the menstrual cycle are conflicting because of differences in the definitions of the menstrual period, outcome measures and types of experimental pain stimulation. So far, there have been only a few studies correlating experimental pain with the levels of gonadal hormones over the menstrual cycle. Therefore, we assessed the responses to multiple experimental pain stimuli during the menstrual cycle and computed their correlations with the salivary concentrations of the gonadal hormones estrogen and testosterone.

Methods: Twenty-four healthy and regularly menstruating women between 20 and 41 years old took part in the study. Detection thresholds (warmth, cold and electrical current) and pain thresholds (cold, heat, pressure and electrical current) were assessed on days 1, 4, 14 and 22 of the menstrual cycle. In each session, salivary samples were collected for the determination of the physiological estrogen 17beta-estradiol, progesterone and testosterone. Progesterone was used exclusively to verify regular menstrual cycling.

Results: Significant variations in pain thresholds for cold, pressure and electrical stimuli were observed over the menstrual cycle with the highest thresholds on day 22, except for the cold pain thresholds, which peaked on day 14. There were no such changes regarding heat pain and all the detection thresholds. The correlations separately computed for each of the 4 days between salivary estrogen as well as testosterone on the one hand and the detection or pain thresholds on the other hand failed to show significant levels, except for the coupling of testosterone and electrical pain thresholds on day 1.

Conclusions: The pain thresholds for all the physical stressors increased after menstruation. The acrophases were located in the follicular (cold pain threshold) or in the luteal phase (pressure and electrical pain thresholds). The results of our correlation analyses indicate only minimal influences of the physiological levels of gonadal hormones on pain sensitivity in women.