Circulus vitiosus is colloquially known as a vicious circle. It is a pathophysiological process that leads to disease or exacerbates existing disease.
What is the circulus vitiosus?
An example of diseases that are based on a vicious circle or in which a vicious circle develops during the course of the disease is diabetes mellitus type 2. The term circulus vitiosus comes from Latin. ‘Circulus’ means ‘circle’ and ‘vitiosus’ can be translated as ‘harmful’. It is a pathophysiological process that is based on positive feedback. In positive feedback, a quantity has a reinforcing effect on itself. Often, however, in a vicious circle, there are several influencing variables that reinforce each other. Examples of diseases that have an underlying vicious circle or in which a vicious circle develops during the course of the disease include type 2 diabetes mellitus, thyrotoxic crisis, heart failure, and multiorgan failure.
Function and task
Circulus vitiosus has essentially no benefit to the human body because it is a pathophysiological process. Pathophysiology is the study of pathologically altered body functions. The opposite of pathophysiological processes are physiological processes. However, often at the beginning of a vicious cycle is a positively intended bodily reaction. The body tries to correct an error or a disturbance with a certain reaction. However, this mechanism leads to changes that make the basic disorder worse and worse. As a result, the disorder is perpetuated or even exacerbated.
Diseases and disorders
An example of a vicious cycle is insulin resistance in diabetes mellitus type 2. Diabetes mellitus is also popularly known as diabetes. The disease belongs to the group of metabolic diseases and is associated with permanently elevated blood glucose levels. Typical symptoms of the disease are severe thirst, increased urination, susceptibility to infections, fatigue and weight loss. If diabetes is not treated or is treated too late, it can cause numerous damages to the body. The increased blood glucose levels damage the blood vessels in particular. This can lead to diseases of the eyes and kidneys. Diabetic retinopathy is the most common cause of blindness in the Western world. The larger blood vessels are also damaged. Diabetics have an increased risk of suffering a stroke or heart attack. Long before manifest diabetes mellitus type 2 appears, an insulin resistance syndrome is present, sometimes for many years. Hereditary factors and, in particular, obesity appear to play a role in the development of this syndrome. When sugar enters the body with food, it is broken down in the intestine and ultimately ends up as glucose in the blood. Insulin is needed so that the glucose can now move from the blood into the cells. This hormone is produced by the pancreas. In insulin resistance, the cells react less to insulin than the cells of a healthy person. As a result, there is always too much sugar in the blood. In response to this excess sugar (hyperglycemia), the pancreas produces more insulin. The more insulin hits the insulin receptors of the cells, the less they react to it. As a result, less and less sugar is transported into the cells and the blood glucose level continues to rise accordingly. Stimulated by this, the pancreas produces more insulin. In this vicious circle, the cells become more and more insulin-resistant. Another vicious circle is found in heart failure. Heart failure is a weakness of the heart. The heart is no longer able to transport the amount of blood needed by the body. Heart failure can be acute or chronic and can have different causes. Causes of acute heart failure include heart attack or pulmonary embolism. Chronic heart failure can be caused by chronic high blood pressure or lung disease. The lack of pumping action of the heart in heart failure causes a deficiency in the supply of blood to the body. This is registered at various points in the body. In particular, falling blood pressure is interpreted by the receptors as an alarm signal. The body reacts by constricting the blood vessels.The beating force of the heart is also increased; it pumps more strongly, but usually more slowly. This increase in cardiac output is caused by the hormone norepinephrine. Since the stroke volume is permanently too low in heart failure, norepinephrine constantly binds to the heart’s receptors. Similar to the insulin receptors in diabetes mellitus, these eventually become resistant. The beating force thus remains low. The blood vessels, however, still respond to the norepinephrine. They remain constricted. Now the already weak and stressed heart has to pump permanently against a high pressure in the blood vessels. As a result of this vicious circle, the condition of the heart progressively worsens. The thyrotoxic crisis is also based on a vicious circle. In a thyrotoxic crisis, a life-threatening metabolic derailment occurs. In most cases, this derailment occurs on the basis of a pre-existing hyperthyroidism. Normally, only small amounts of the thyroid hormones T3 and T4 are present in the blood. They are predominantly bound to blood proteins. In thyrotoxic crisis, there is a sudden release of unbound thyroid hormones. This results in severe symptoms of hyperthyroidism, such as severe cardiac arrhythmias, hyperthermia, or gastrointestinal symptoms. Through a positive feedback mechanism, these organ complications in turn affect thyroid hormone production. Increased thyroid hormones are produced. These in turn exacerbate the symptoms. Therefore, the goal of therapy is to interrupt the vicious circle of thyrotoxic crisis.
