Cholesterol
Cholesterol is the most abundant cyclic alcohol in the human body and is obtained through diet.
(primarily from animal fats) and is synthesized in the liver (to a lesser extent also in other tissues such as the intestinal mucosa, adrenal glands, ovaries, testes, and placenta). In plasma, cholesterol is present as part of lipoproteins: chylomicrons, very low-density lipoproteins (VLDL), intermediate-density lipoproteins (IDL), low-density lipoproteins (LDL), and high-density lipoproteins (HDL). Approximately 60–70% of cholesterol is contained in LDL and 25–35% in HDL. Cholesterol is excreted from the body mainly as bile acids, with a small portion excreted unchanged in bile. Cholesterol is an essential component of cell membranes and a precursor for the synthesis of several physiologically important steroids, including bile acids, vitamin D, and steroid hormones. Different lipoproteins have distinct functions and associations with cardiovascular risk. While the primary function of LDL is to transport cholesterol to tissues, HDL is responsible for the reverse transport of excess cholesterol back to the liver. The uptake of LDL by macrophages in the arterial wall is a key step in the pathogenesis of atherosclerosis.
When measuring cholesterol levels, the total cholesterol content across different lipoproteins is assessed, and HDL cholesterol and LDL cholesterol can also be measured separately.
Indications and clinical significance
Diagnosis and monitoring of dyslipidemias, as well as assessment of cardiovascular risk in combination with other risk factors (see also Triglycerides).
Higher-than-recommended total cholesterol and/or LDL cholesterol levels and lower HDL cholesterol levels increase the risk of cardiovascular diseases.
Cholesterol levels may increase due to a diet rich in fats and cholesterol, as well as in conditions such as cholestasis, nephrotic syndrome, chronic kidney disease, hypothyroidism, diabetes, and obesity. During pregnancy, cholesterol levels may also be higher than usual. Among genetic factors, mutations in the LDL receptor gene (familial hypercholesterolemia) are the most significant, in which case cholesterol levels may already be elevated to 7.5–12 mmol/L at an early age.
Reduced cholesterol levels may occur in cases of malnutrition, malabsorption syndromes, high intake of plant-based fats, malignant tumors, liver cirrhosis, and hyperthyroidism.
In different primary dyslipidemias, HDL and LDL cholesterol levels change in different ways. For example, familial hypercholesterolemia is characterized by elevated LDL cholesterol, while hyperalphalipoproteinemia is characterized by increased HDL cholesterol. Moderately to markedly elevated LDL cholesterol levels may also occur secondarily in various conditions such as diabetes, hypothyroidism, nephrotic syndrome, chronic kidney disease, and during pregnancy. Reduced LDL cholesterol levels may be observed in severe systemic illnesses, with the use of certain medications, and in some rare inherited lipoprotein deficiencies (abetalipoproteinemia, hypobetalipoproteinemia). Elevated HDL cholesterol levels may be caused by certain medications (e.g. estrogens, antiepileptic drugs, bronchodilators), pregnancy, and chronic excessive alcohol consumption. Decreased HDL cholesterol levels may occur in acute illnesses, including myocardial infarction and stroke, major trauma, recent surgery, diabetes, nephrotic syndrome, chronic kidney disease, hypothyroidism, liver diseases, anemias, myeloproliferative disorders, Tangier disease, and others.
The Terviseuuringud.ee Health Check Plus package includes cholesterol testing (including HDL and LDL).
Cholesterol testing can also be added to all other packages.