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Endothelial dysfunction

The single-cell layer that lines every blood vessel — the endothelium — is more than plumbing. When it stops doing its regulatory jobs properly, the result is impaired vasodilation, increased inflammation, and a pro-clotting state. This pattern is studied across cardiovascular disease, diabetes, and long COVID.

Edited by M. Callahan · Last reviewed 2026-05-10

How researchers study it

Endothelial function can be measured non-invasively by flow-mediated dilation (FMD) — using ultrasound to assess how an artery responds to increased blood flow. In experimental settings, biomarkers in serum (von Willebrand factor, soluble ICAM-1, endothelin-1) and circulating endothelial cells provide complementary measures. The classic textbook for the field is built around the work of Furchgott, Ignarro, and Murad on nitric oxide, which earned them the 1998 Nobel Prize (Nobel Foundation, 1998).

In COVID-19, autopsy and imaging studies have shown direct evidence of endothelial inflammation and microvascular injury in severely ill patients. A widely cited 2020 paper in The Lancet reported viral inclusions in endothelial cells and diffuse endothelial inflammation in COVID-19 fatalities (Varga et al., Lancet, 2020, PubMed 32325026). Subsequent work has expanded the picture to include microclots, capillary dropout, and impaired flow-mediated dilation in patients with long COVID (Charfeddine et al., Frontiers in Cardiovascular Medicine, 2022, PubMed 35538015).

Endothelial-dysfunction-as-mechanism is one of several hypotheses for symptoms in long COVID — particularly for exercise intolerance, palpitations, and possibly for cognitive symptoms via cerebral microvascular changes. It is not the only hypothesis, and the field has not closed on a single mechanism.

Common misconceptions

"Endothelial dysfunction is the same as atherosclerosis."Endothelial dysfunction is an early functional change that can precede and contribute to atherosclerosis, but the two are distinct.
"You can self-test endothelial function at home."Validated measurement requires ultrasound (FMD) or laboratory biomarkers. Consumer wearables and "vascular age" estimates from various devices have varying validation.
"A specific supplement reverses endothelial dysfunction."Lifestyle interventions — exercise, smoking cessation, Mediterranean-style diet, sleep, blood pressure control — have the strongest evidence base. Specific supplement claims are mostly under-studied.
WHAT THIS DOES NOT MEAN This entry describes a vascular research area. It is not a diagnosis. Cardiovascular symptoms and elevated risk factors need clinical evaluation — endothelial function is one of many considerations and is not assessed in isolation.
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SOURCES
  1. Nobel Foundation. "The Nobel Prize in Physiology or Medicine 1998." nobelprize.org
  2. Varga Z et al. "Endothelial cell infection and endotheliitis in COVID-19." Lancet, 2020. PubMed: 32325026
  3. Charfeddine S et al. "Long COVID 19 Syndrome: Is It Related to Microcirculation and Endothelial Dysfunction?" Frontiers in Cardiovascular Medicine, 2022. PubMed: 35538015
Informational only · Not medical advice This entry describes vascular biology research. It does not diagnose, treat, cure, or prevent any disease. Cardiovascular concerns need clinical evaluation.