Napier C, Allinson K, Gan EH, et al. - This study was undertaken to determine steroidogenic function in autoimmune Addison disease, a rare endocrinopathy characterized by immune-mediated destruction of the adrenal cortex, immediately following diagnosis and during prolonged treatment. In response to ACTH_1-24, the authors studied peak serum cortisol in 20 newly diagnosed patients with autoimmune Addison disease at first presentation and then again within a month. In addition, they analyzed 37 patients with established Addison disease (for between 7 months and 44 years) in a medication-free state, measuring peak serum cortisol responses to ACTH_1-24 and the urine LC-MS steroid metabolome. Autoimmune Addison disease is a heterogeneous disorder, displaying a rapid decline in adrenal steroidogenesis in the first few weeks after diagnosis with low-level residual activity in a minority of patients, which seems to continue for several years.