We report the case within a 22-year-old patient, initially seen because of fatigue, weight loss and discoloration of the skin. A Hashimoto-Thyroditis had been diagnosed a few months prior to the clinical presentation. Blood samples showed a hyponatremia and hyperkalemia. Addison's disease was diagnosed by management of cortisol, ACTH and adrenal antibodies. In combination with the previously diagnosed Autoimmune thyreoiditis the criteria for a Schmidt's Syndrome were fulfilled. We initiated the substitution of Hydrocortisone (20 mg/d) and Fludrocortisone (0.1 mg/d) in combination with an increased levothyroxin-dosage (100 µg/d). The patient's condition improved over the course of a few days. The presented case underlines the importance of focused examinations and diagnostics when dealing with a patient with unspecific symptoms and a pre-existing autoimmune disease. This also applies to patients with a positive family history for autoimmune disorders.