['The term "adrenal fatigue" ("AF") has been used by some doctors, healthcare providers, and the general media to describe an alleged condition caused by chronic exposure to stressful situations. Despite this, "AF" has not been recognized by any Endocrinology society, who claim there is no hard evidence for the existence. The aim of this systematic review is to verify whether there is substantiation for "AF".', 'A systematic search was performed at PUBMED, MEDLINE (Ebsco) and Cochrane databases, from the beginning of the data until April 22nd, 2016. Searched key words were: "adrenal"\u2009+\u2009"fatigue", "adrenal"\u2009+\u2009"burnout", "adrenal"\u2009+\u2009"exhaustion", "hypoadrenia", "burnout"\u2009+\u2009"cortisol", "fatigue"\u2009+\u2009"cortisol", "clinical"\u2009+\u2009"burnout", "cortisol"\u2009+\u2009"vitalility", "adrenal"\u2009+\u2009"vitality", and "cortisol"\u2009+\u2009"exhaustion". Eligibility criteria were: (1) articles written in English, (2) cortisol profile and fatigue or energy status as the primary outcome, (3) performed tests for evaluating the adrenal axis, (4) absence of influence of corticosteroid therapy, and (5) absence of confounding diseases. Type of questionnaire to distinct fatigued subjects, population studied, tests performed of selected studies were analyzed.', 'From 3,470 articles found, 58 studies fulfilled the criteria: 33 were carried in healthy individuals, and 25 in symptomatic patients. The most assessed exams were "Direct Awakening Cortisol" (n =\u200929), "Cortisol Awakening Response" (n =\u200927) and "Salivary Cortisol Rhythm" (n =\u200926).'] Does adrenal fatigue exist : a systematic review?