Premenstrual asthma: epidemiology, pathogenesis and treatment.

The exacerbation of asthma in the premenstrual period has long been of interest. Premenstrual asthma has been estimated to affect up to 40% of females with asthma, although the exact prevalence of this phenomenon is unclear as studies have involved small numbers in hospital clinics. Large-scale community-based studies are required to estimate its true prevalence. Researchers are slowly piecing together clues as to the aetiology and pathogenesis of the disorder. Female sex-steroid hormones play an important role but the exact mechanism is still unknown. Recent evidence suggests that increased airway hyperresponsiveness, an indicator of underlying airway inflammation, during the luteal phase of the menstrual cycle may account for premenstrual exacerbations. In addition, there is now evidence of impaired or altered beta2-adrenoceptor function and regulation in females with asthma, which may have a part to play. Accurate diagnosis is dependent on a detailed history and the demonstration of premenstrual dip in peak expiratory flow. Exacerbations in the majority of women will respond to the usual treatment of bronchial asthma. However, a few women will experience significant morbidity or treatment-related adverse effects. Case reports suggest that the combined oral contraceptive pill or gonadotrophin-releasing hormone analogues may be effective in these patients. This requires substantiation by randomised controlled trials.