Cortisol, a glucocorticoid (GC) hormone secreted from the adrenal glands, is essential for survival. Cortisol also possesses anti-inflammatory actions and GC formulations (prednisolone) are used to treat many inflammatory diseases and conditions. Indeed, three percent of the Danish population (≈ 180.000 individuals) redeems at least one prescription of synthetic GC per year and at least 20,000 patients annually discontinue GC treatment. Pharmacological GC therapy suppresses endogenous cortisol production and thereby induce relative adrenal insufficiency (GIA). The risk of GIA as determined by the adrenal corticotrophic hormone (ACTH) stimulation test has previously been reported to ≈ 25 %, but testing after GC treatment is not routinely performed. Indeed, new evidence suggest that the risk of GIA after planned cessation of prednisolone treatment for polymyalgia rheumatic (PMR) or giant cell arteritis (GCA) is substantially lower, probably 2%. The reason for this discrepancy is undoubtedly selection bias in the previous publications and the use of inaccurate cortisol assays. At the same time, however, it was observed that 25% exhibited pronounced symptoms of adrenal insufficiency based on a questionnaire specific for detecting symptoms of adrenal insufficiency, the so-called AddiQoL-30. Concomitantly, the basal cortisol levels in the same group were significantly lower as compared to the group, who exhibited milder or no symptoms attributable to adrenal insufficiency. This observation aligns with the clinical experience that PMR/GCA patients often complain of fatigue after planned cessation of prednisolone treatment. This often occurs in the absence of objective symptoms or signs of residual PMR/GCA disease activity. The scenario has been designated as the steroid withdrawal syndrome. This may represent a state of relative adrenal insufficiency prompted by long term, high dose prednisolone treatment. The proper way to tackle this clinical conundrum is to perform a proper randomized trial, which so far has not been conducted. Therefore, investigators of this study will perform the first placebo-controlled randomised controlled trial (RCT) in patients with PMR and GCA after planned cessation of GC treatment. Investigators argue that neither watchful waiting nor routine hydrocortisone replacement are infallible. The study will be the first evidence-based guidance and aid to GIA patients and thus meet an important need for many thousand patients.