Asthma is a chronic inflammatory lung disease characterized by airway hyper-responsiveness and reversible airway obstruction. Over the last decade, the prevalence of asthma is on the rise and it disproportionately affects more women than men. As much as 40% of women with asthma are known to have worsening of asthma symptoms and lung function prior to menstruation. This syndrome is being increasingly recognized as premenstrual asthma (PMA). The pathologic differences in female asthmatics with and without this syndrome are not known. The evidence regarding the role of sex hormones has been contradicting. We propose an observational cohort study to examine the changes in airway inflammation in women with asthma in relation to their menstrual cycle and their association with sex hormone levels. In addition we will include women on oral contraceptives to determine their effect on airway inflammation and asthma symptoms.

We hypothesis that:

• Women with premenstrual asthma will show increased indices of airway inflammation in various phases the monthly menstrual cycle.
• In women with premenstrual asthma, a change in serum estradiol/progesterone ratio during the late luteal phase is associated with worsening of airway inflammation, air flow limitation and asthma symptoms.
• The use of oral contraceptives is associated with suppression of the cyclical changes in airway inflammation due to lack of fluctuations in estradiol and progesterone levels.

Recruited subjects will be asked to record asthma symptom scores, morning Peak Expiratory Flow Rate (m-PEFR) and rescue asthma medication (β2-agonist) used daily during the one month screening period to identify women with and without pre-menstrual asthma. Asthmatic women with regular menstrual cycles will be evaluated in their follicular phase (days 5-8) and luteal phase (days 21-24) and women on oral contraceptive pills (OCP) will be evaluated on days 9-12 of their OCP cycle and during the days 25-28, off of OCP consecutively for a 2-month period.

Inclusion Criteria:

• With diagnosis of Asthma (ICD-9 Code 493)
• Requiring low to moderate dose inhaled corticosteroids for control.
• With Pre-bronchodilator FEV1 ≥50% and ≤90% of predicted normal
• With a positive bronchodilator response
• Non smoker or Ex-smoker (Quit >1 year ago)
• Regular menstrual cycle (24-35 days cycle)
• With and without OCP use
• Constant dose of asthma maintenance medication for at least 30 days prior to enrolment

Exclusion Criteria:

• Recent use of systemic steroids (<30 days)
• Severe Asthma (FEV1 <50% or frequent exacerbations or systemic steroid dependence)
• Negative bronchodilator response
• Current Smoker
• Irregular Menses or postmenopausal
• Positive pregnancy test
• Use of hormonal contraceptives other than monophasic OCPs
• Exacerbation or Respiratory Infection or antibiotic use within the last 30 days

Females diagnosed with asthma, with either regular menstral cycles or on monophasic oral contraceptives, with or without pre-mentstual asthma symptoms