In difficult-to-manage asthma, effective control depends on identification and alleviation of exacerbating factors, such as ongoing allergen exposure, chronic sinusitis, GERD, and emotional stress. Level of compliance with the prescribed medication regimen should be evaluated in all patients. Hormonal factors (i.e., menses, use of exogenous hormones by female patients, and hyperthyroidism) also can exacerbate asthma. When aggressive management fails, the possibility of a misdiagnosis should be considered. Other conditions that can mimic asthma include COPD, congestive heart failure, airway obstruction due to various causes, vocal cord dysfunction, and esophageal spasm. Referral to an asthma specialist is advised in severe or resistant cases.