Inclusion Criteria:  BMI 18.5 - 25 kg/m2  Exclusion Criteria:  Previous medical history for any chronic condition in the last three months, active disease or abnormal physical examination as verified by a qualified physician. Casual smoking (>6 cigarettes per day) Frequent, heavy alcohol consumption (>30g/day) Frequent, heavy caffeine consumption (>4 caffeinated drinks/day) Regular physical exercise (>4hrs per week) Shift workers Participation in an investigational drug trail within the past two months Intake of any drugs (prescribed, over the counter or recreational) including topical steroids and inhalers, within 48 hours of the study initiation Known allergy to metyrapone Inability or unwillingness to provide informed consent