Despite optimized hydrocortisone replacement regimes, many patients with adrenal insufficiency (AI) suffer from impaired quality of life (QoL). Characteristically, patients report high fatigue levels at certain times during the day. A modified-release hydrocortisone has been shown to improve QoL, particularly fatigue, in patients with primary AI. However, it is unknown, if the same effect can be observed in patients with secondary AI. Further, no studies have evaluated the effect, taking into account the diurnal variation of fatigue. A novel survey method termed Ecological Momentary Assessments (EMA) has the potential to provide reliable measurements of diurnal variations in patient-reported outcomes, such as fatigue. We will compare the effect of modified-release compared to conventional hydrocortisone on fatigue in patients with secondary AI due to pituitary disease, and hereby assess the feasibility of EMA as outcome in future large-scale randomised clinical trials (RCTs).