ISCHEMIC BUT NOT THERMAL PAIN SENSITIVITY VARIES ACROSS THE MENSTRUAL-CYCLE

Objective and Method: Findings from both animal and human research sug gest that pain sensitivity changes across the menstrual cycle; however , among humans the nature of these menstrual cycle effects remains unc lear. The present study used a repeated-measures design to evaluate ch anges in thermal and ischemic pain responses during three phases of th e menstrual cycle, midfollicular (postmenstrual), ovulatory, and mid-t o-late luteal (premenstrual), in 11 healthy women. The cycle phase dur ing which subjects began their participation was determined randomly. Plasma levels of estrogen, progesterone, luteinizing hormone (LH), tes tosterone, and beta-endorphin were determined at each experimental ses sion. Participants also completed a daily diary of physical and emotio nal symptoms for two complete menstrual cycles before the experimental sessions. Results: The results indicated that women showed less ische mic pain sensitivity during the midfollicular compared with the ovulat ory and mid-to-late luteal phases, but thermal pain responses did not vary significantly across menstrual cycle phases. Physical and emotion al symptoms were minimal and did not change significantly across the m enstrual cycle. Conclusions: These findings indicate greater ischemic but not thermal pain sensitivity among women after the midcycle LH sur ge, The practical relevance and potential mechanisms of these findings are discussed.