Ovarian hormones and pain response: a review of clinical and basic science studies.

BACKGROUND: Most clinical pain disorders are more common in women than in men, particularly during the peak reproductive years. This suggests that fluctuations in the ovarian hormones encountered during the female menstrual cycle may increase pain response.
OBJECTIVES: This article examined whether pain severity and experimental pain thresholds vary during the phases of the menstrual cycle in women with and without clinical pain disorders. It also reviewed the effect of ovarian hormones on behavioral responses to painful stimuli (pain reactivity) in animal models and the potential mechanisms through which ovarian hormones modulate pain reactivity.
METHODS: A narrative review was performed to ascertain the relationship between ovarian hormones and pain response. Relevant English-language publications describing pain reactivity in premenopausal women and female rodents were identified through searches of MEDLINE and PubMed from January 1, 1967, through May 1, 2008, as well as through the reference lists of identified articles.
RESULTS: In the clinical studies reviewed, most pain disorders were reported to worsen during the late luteal and early follicular phases of the menstrual cycle. Pain thresholds and tolerance times also varied during different phases of the menstrual cycle in healthy premenopausal women in the majority of studies. Basic science studies suggested that ovarian hormones have distinct effects-on inflammation, affective states, stress responses, modulatory pain systems, and afferent sensory systems-that increase or decrease pain reactivity.
CONCLUSIONS: Fluctuations of ovarian hormones in the course of the menstrual cycle appear to be associated with a mild to moderate effect on pain response. Greater knowledge of the mechanisms by which ovarian hormones modulate pain would broaden our understanding of why pain disorders are more frequent, severe, and disabling in women than in men.