Sensory changes during the ovulatory phase of the menstrual cycle in healthy women

This study compared the pain sensitivity in healthy women at the abdomen an d lower back (presumed referral areas of menstrual pain), thigh and arm (co ntrol areas), in the menstrual, ovulatory, luteal and premenstrual phases o f confirmed ovulatory cycles, with that of males. The pressure pain thresho ld (PPT) and pinch pain threshold (PiPT) was determined by an electronic pr essure algometer, heat pain threshold (HPT) by a contact thermode and tacti le threshold (TT) with von Frey hairs. The abdominal PPT was significantly lower in females in all menstrual phases as compared to the control sites ( p <0.0007). The abdominal and lower back HPT was significantly lower in fem ales in all menstrual phases compared with control areas, and to the sites in males (p <0.002). The TT was significantly reduced in females compared w ith males (p <0.013). There was no difference in the PiPT between females a nd males. In males, the HPT, PPT and TT were not different Within any site. During the ovulatory phase, the HPT was significantly reduced at the abdom en and the PPT at the back compared with the menstrual, luteal and premenst rual phases (p <0.0002). There were no within-menstrual phase variations in the PiPT and TT at any site, or for the HPT and PPT at the control areas. The reduced thresholds in menstruating women may be due to the presence of latent uterine algogenic stimuli, and the increased levels of oestrogen and leuteinizing hormone at ovulation may enhance nociception by acting both a t the peripheral and central level, resulting in the hypersensitivity chang es at the abdomen and lower back areas. (C) 2001 European Federation of Cha pters or the International Association for the Study of Pain.