This study proposes to provide the reference range of cortisol results when the ACTH stimulation test is done under stressful conditions. This important information is currently not available in the literature. To achieve this, we will perform the ACTH stimulation test in a cohort of patients who are booked for elective surgery. By choosing elective surgery patients, we afford ourselves the opportunity of performing the test once before surgery. The test is then repeated within 12 hours of surgery. The first test will be done on an out-patient basis under usual conditions (minimal stress) while the second will be done under intense physical stress. The 2 sets of results will be compared and the effect of stress on test results will be determined. For the sake of uniformity, we have chosen patients who are booked to undergo repair of an abdominal aortic aneurysm (AAA) as our study cohort.