"Kryptopyrroluria (KPU) and hemopyrrolactamuria (HPU) are common but often overlooked disorders of cellular metabolism. A variety of diseases correlate with KPU or HPU or can be a direct consequence, e.g. histamine intolerance, anxiety/depression, thyroid disorders (Hashimoto thyroiditis), chronic fatigue states with or without adrenal insufficiency. Already the physician Carl Pfeiffer, MD, the discoverer of KPU, estimated that more than 10% of the population is affected by KPU. The authors have been treating people with KPU and HPU for years and believe that they should be seen as independent factors in many chronic diseases. From their own therapeutic experience with many hundreds of patients, they have developed a comprehensive diagnostic and therapeutic concept ("4-E- program") that provides effective treatment.