Hypercholesterolemia

HYPERCHOLESTEROLEMIA, HYPERCHOLESTERINEMIA, increase and decrease in the content of cholesterol in the blood. Cholesterol (see) in the blood occurs as an obligatory component—in a free state and in combination with fatty acids (esters). The plasma contains both free cholesterol and especially its esters; the red blood cells, however, contain almost exclusively free cholesterol. In red blood cells, the amount of cholesterol is slightly greater than in the plasma. In healthy individuals, cholesterolemia fluctuates from 1% to 2%. In individuals of an asthenic constitutional type, it is generally lower (on average 1.3%), while in individuals of a hypersthenic type, it is higher (on average 1.8%). Nutritional conditions exert a known influence on cholesterolemia. For example, among the population of the Dutch East Indies (which eats rice), cholesterolemia has a low level. During chronic undernutrition, cholesterol in the blood decreases. After a meal rich in cholesterol (egg yolks, brains, animal fat), cholesterolemia may sometimes increase (during the first few hours), but this is by no means a rule. A persistent increase in it in healthy individuals has not yet been achieved even with the ten-day administration of large doses of cholesterol. The endocrine influences on cholesterolemia are physiologically evident in women: during pregnancy, cholesterolemia shows a distinct tendency to increase (this is also noticeable to a slight extent during menstruation and the climacteric). According to the view of Chauffard, this is explained by the fact that the corpora lutea of the ovaries (and the adrenal glands) possess the ability to produce cholesterol. This fact is merely an example of endocrine influences on cholesterol metabolism: after extirpation of the thyroid gland and in myxedema, cholesterol in the blood increases, while in hyperthyroidism it is sometimes decreased, etc. In liver diseases, cholesterolemia increases during jaundice of a mechanical nature* (closure of the ducts by a tumor, a stone)—up to 6%. This is explained by the fact that the liver is an organ that excretes cholesterol from the body. Cholesterol in the blood may also increase in certain diseases of liver cells. But in acute and severe lesions of the hepatic parenchyma (yellow atrophy, syphilitic-salvarsan jaundice), during the acute phase of the disease, a decrease in cholesterolemia is observed (down to 0.6%)—a fact which, in connection with others, raises the question of whether the liver is an organ that participates in the formation of cholesterol. In so-called catarrhal jaundice, cholesterol in the blood does not increase at all in parallel with bile pigments and acids, and is often even decreased. The influence of constitutional factors on cholesterolemia is particularly evident in diseases a) of metabolism and b) of the vessels. Gout and obesity are often accompanied by hypercholesterolemia. Some gallstones consist almost entirely (99%) of cholesterol (Aschoff). At one time, a theory was advanced that gallstones are formed as a result of excessive excretion of cholesterol by the liver; this view was supposed to be confirmed by hypercholesterolemia (as a cause of stone formation), which is observed in such cases. However, it is observed mainly in arthritics, and in other cases the content of cholesterol in the blood and in the bile may be normal, which is why stone formation in these cases must be connected with other changes in the bile (due to stasis, infection, etc.). The greatest significance is attached to cholesterolemia in atherosclerosis. First, it has been proven that its development is connected with the infiltration of cholesterol and other lipoids into the intima; secondly, Russian pathologists (Anichkov, Khalatov, Ignatovsky, etc.) succeeded in inducing experimental atherosclerosis in rabbits (and other animals) by feeding them cholesterol. Since a sharp hypercholesterolemia developed in this case, the view was expressed that in humans, atherosclerosis is also a consequence of excessive cholesterol content in the blood. In atherosclerosis, hypercholesterolemia is indeed observed, but by no means as a rule. It must be admitted that the deposition of cholesterol in the intima can occur even with a normal content of cholesterol in the blood. Consequently, the basis of the disease must also lie in local conditions on the part of the vessel, which favor the deposition of cholesterol. There are other examples of local deposits of cholesterol (often, but not necessarily, accompanied by hypercholesterolemia): xanthoma of the skin, etc., and arcus corneae senilis (the latter, however, occurs not only in old age, but sometimes already in youth). Some tend to unite these diseases (atherosclerosis and cholelithiasis) under the concept of "cholesterol diathesis."—Hypercholesterolemia was also found in essential hypertension (it was considered the cause of increased blood pressure), but cholesterolemia is moderately increased only in hypertensives belonging to a certain morphological type, namely, the hypersthenic type, and reflects