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What is hypercholesterolemia, its causes and types?

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endogenous synthesis of the organism

Cholesterol is a fatty substance found in the body. Therefore performing and regulating functions such as forming bile acids or hormones (such as sexual or thyroid hormones) is necessary. However, although it is essential, its high numbers are also a risk factor for certain heart diseases.

Hypercholesterolemia occurs when the presence of cholesterol in the blood is above levels considered normal. This increase is associated with coronary problems, the type of diet, the sex of the person, the lifestyle and the endogenous synthesis of the organism.

Hereditary and dietary factors are involved in cholesterol concentration in the blood and other related physical activity.

Causes

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Among the factors that influence the increase in cholesterol levels are:

Inadequate diets: Abusing animal fats or alcohol causes the body to consume other nutrients first, favouring that cholesterol does not degrade and accumulates in the arteries.

Liver, endocrine and kidney diseases and the administration of certain substances increase the synthesis of LDL lipoproteins, which transport cholesterol harmful to the body.

Familial hypercholesterolemia: This is a hereditary disease caused by a genetic defect that prevents LDL cholesterol from being broken down, causing cholesterol levels to increase progressively. In these cases, early mortality due to myocardial infarction or thickening of the arteries caused by atherosclerosis is frequent.

Types

The volume of circulating cholesterol depends on its intestinal absorption, endogenous synthesis, tissue uptake, the state of lipoprotein metabolism, and biliary excretion. Ultimately, the cholesterol level will depend on the food eaten and the absorption capacity of specific receptors. Likewise, two types of hypercholesterolemia can be distinguished:

Primary: derived from problems in the cholesterol transport systems and genetic factors. Dyslipidemias are framed in this type of hypercholesterolemia.

Secondary: increased cholesterol is associated with certain liver diseases (hepatitis, cholestasis and cirrhosis ), endocrine diseases ( diabetes mellitus, hypothyroidism and anorexia nervosa) and kidney diseases (nephrotic syndrome or chronic renal failure). In addition, some substances can increase the levels of LDL cholesterol (low-density cholesterol known as ‘bad cholesterol), favouring the development of hypercholesterolemia, such as anabolic steroids, progestogens, beta-blockers and some hypertensive substances.

Serious forms:

Numerous disorders can cause severe hypercholesterolemia, although its development is usually due to genetic factors. The most important forms of cholesterolemia are familial hypercholesterolemia, severe polygenic hypercholesterolemia, and combined familial hypercholesterolemia.

Familial hypercholesterolemia

It is a severe disorder caused by a series of mutations in the receptor gene for low-density lipoproteins that transport cholesterol. It affects one in 500 people, and experts estimate that more than one million Spaniards suffer from familial hypercholesterolemia, although 70 per cent of them are neither diagnosed nor treated. In addition, there are heterozygous and homozygous forms of the disease. In the heterozygous state, the patient has only half the usual number of LDL receptors detected in neonates.

In these cases, the cholesterol level is between 300 and 500 milligrams per deciliter (mg/dl). The consequence of this disorder is the development of early coronary disease, which in men appears between the fourth and fifth decade of life. In women, it manifests itself a decade later. According to the latest studies, 75 per cent of untreated men with familial hypercholesterolemia will have a heart attack before the age of 60 and women before the age of 70. In addition to diet, this form of hypercholesterolemia requires pharmacological treatment.

Most patients respond to monotherapy with resins, nicotinic acid or statins, although in severe cases, two or even all three substances are necessary for combination. In the homozygous form, there is an almost complete absence of the cell surface that LDL clears. It occurs in one in every million inhabitants, and those affected have a cholesterol concentration between 700 and 1,200 mg/dl. The receptors’ low activity causes them to resist diets and drugs designed to reduce cholesterol levels. Probucol is used to treat this disorder, although liver transplantation has also been used to supply the missing LDL receptors. This treatment reduces LDL cholesterol and increases the response to hypocholesterolemic drugs. However, it requires close control of the transplanted organ, for which continuous immunosuppression is needed.

Severe polygenic hypercholesterolemia

It is characterised by an elevated level of LDL cholesterol caused by genetic and environmental factors. It is associated with an increased risk of cardiovascular disease, and about seven per cent of first-degree relatives of patients with polygenic hypercholesterolemia have significant concentrations of LDL cholesterol. The level is usually above 220 mg/dl. The treatment is based on administering resins, nicotinic acid and statins. The combined administration of the three substances is generally not necessary.

Familial combined hyperlipidemia

In this disorder, those affected have very high levels of cholesterol or triglycerides. It is unknown if the cause is found in one or several genetic factors, and there are no clinical features that allow it to be diagnosed. Total cholesterol is between 250 and 350 mg/dl, while triglycerides undergo significant variations. The treatment consists of reducing weight and the intake of saturated fats and cholesterol.

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