Endothelium

The inner lining of the vessels — the first line of defense against atherosclerosis.

The endothelium is the thinnest layer of cells lining the inside of the vessels. It is not just "wallpaper": the endothelium actively controls vascular tone, clotting and inflammation by producing nitric oxide (NO) — a molecule that relaxes the arteries.

When the endothelium is damaged (endothelial dysfunction), the vessels dilate less well and inflame more easily — this is the earliest stage of atherosclerosis, long before plaques appear.

Reference ranges

The endothelium is assessed functionally; there is no numeric "normal range" as for a lab test:

Healthy endothelium	good NO production, vessels dilate
Endothelial dysfunction	reduced vessel dilation (by FMD)
Assessment method	flow-mediated dilation (FMD) of the brachial artery
Significance	an early, reversible stage of atherosclerosis

Important: Endothelial dysfunction is partly reversible: unlike established plaques, at an early stage vessel function can be improved through lifestyle.

What an elevated level means

The "bad" state is endothelial dysfunction: the cells make less nitric oxide, the vessels dilate less well, and inflammation and a tendency to thrombosis increase.

This is an early, still-reversible forerunner of cardiovascular disease. The endothelium is damaged by the same factors as the vessels overall: high blood pressure, smoking, high LDL, diabetes, physical inactivity.

What a low level means

The "good" state is a healthy, working endothelium: it makes enough nitric oxide, keeps the vessels relaxed and protects them from inflammation and clots.

Endothelial function is improved by aerobic exercise, a Mediterranean-style diet, control of blood pressure, cholesterol and blood sugar, quitting smoking and enough sleep.

How the test is done

In research, endothelial function is assessed by flow-mediated dilation (FMD) of the brachial artery on ultrasound, and by biomarkers. In routine practice it is rarely measured separately.

In practice, endothelial health is judged indirectly — from risk factors and the state of the vessels (blood pressure, cholesterol, arterial stiffness).

What affects the value

Aerobic exercise — improves endothelial function (more NO).
Smoking — badly damages the endothelium.
High LDL and diabetes — impair function.
High blood pressure — damages the vessel lining.
Diet (vegetables, nitrates, omega-3) — supports NO.
Chronic inflammation and stress — worsen it.

Estimate your vascular age

Endothelial function is reflected in the vessels' "age" — assess it:

Vascular Age (FMD) Vascular age from endothelial function (%FMD), body composition, and biomarkers — the Everist VAC model Open Vascular Age (ADVANT'AGE) Vascular age and 5-year cardiovascular risk from blood pressure, cholesterol, glucose, and creatinine — the ADVANT'AGE model Open

Frequently asked questions

What is endothelial dysfunction?

It is a state in which the inner lining of the vessels makes less nitric oxide and relaxes the arteries less well. It increases inflammation and the tendency to thrombosis and is regarded as the earliest, still-reversible stage of atherosclerosis.

Why does the endothelium need nitric oxide?

Nitric oxide (NO) is a signalling molecule made by a healthy endothelium. It relaxes the muscle in the vessel wall, widens the arteries, lowers blood pressure and prevents platelets from clumping. A drop in NO production is the key to vascular dysfunction.

Can the endothelium be restored?

At an early stage — largely yes. Aerobic exercise, a healthy diet, quitting smoking and control of blood pressure, cholesterol and blood sugar improve endothelial function. This is one reason lifestyle has such a strong effect on vascular health.

Sources

info

This content is educational and does not replace consultation with a physician. Reference ranges may vary depending on the laboratory and method — rely on the ranges stated on your own test report.

← All glossary terms