Total cholesterol

The sum of all cholesterol fractions. On its own it says little – for interpretation the individual fractions such as LDL and HDL are looked at.

What cholesterol does in the body

Cholesterol is a building block of every cell membrane: it sits between the phospholipids and regulates how firm or flexible the membrane is. From cholesterol, the liver makes bile acids for fat digestion, the adrenal glands and gonads make cortisol, aldosterone and sex hormones, and in the skin vitamin D is formed from a precursor. Most of it is made in the body itself, above all in the liver, from acetyl-CoA; the rate-limiting step is the enzyme HMG-CoA reductase. When a cell's cholesterol content falls, it activates its own production and more LDL receptors via the switch SREBP-2. Bile acids and cholesterol are largely recovered in the gut and circulate between the gut and the liver.

Low total cholesterol – what happens in the body?

A low total value shows that little cholesterol is travelling in the blood's lipoproteins – because the liver is producing little or taking the particles back up quickly. This occurs with an overactive thyroid, which increases the number of LDL receptors, and also with malnutrition, severe liver disease, disorders of fat absorption and in acute or chronic inflammation, during which cholesterol falls temporarily. The production of steroid hormones usually remains secure, because the adrenal glands and gonads also make cholesterol themselves. Inherited disorders of cholesterol production, which become apparent in childhood, are very rare.

High total cholesterol – what happens in the body?

The total value is the sum of the cholesterol in LDL, HDL and the triglyceride-rich particles. A high value can therefore come about in different ways: through a lot of LDL, a lot of HDL or plenty of VLDL remnants. When it rises because of LDL, the particles stay longer in the blood because the liver takes them up more slowly via the LDL receptor, and more cholesterol is deposited in the inner vessel wall; at very high values it can also become visible as yellowish deposits on the eyelids and tendons. Causes include inherited variants, an underactive thyroid, the drop in oestrogen after the menopause, bile congestion, kidney disease and pregnancy.

The interpretation is given in your report.