This book is aimed at all those interested in exploring new methods for diagnosing adrenal insufficiency, particularly in the current context of the COVID-19 pandemic. Adrenal insufficiency is a complex medical condition that requires accurate diagnosis for effective treatment. Current diagnostic methods, while useful, have certain limitations. This book presents a promising new method for diagnosing adrenal insufficiency, involving the use of 61Cobalt-labeled eplerenone and MRI.In the context of the COVID-19 pandemic, this method could prove particularly useful, as the virus can affect blood pressure regulation and potentially cause conditions such as hypertension or hypotension.We hope this book will be a valuable resource for those seeking to improve the diagnosis and treatment of adrenal insufficiency.