Does estradiol in men help maintain HDL levels and vascular endothelial protection?

In men, estradiol (E2) plays a critical role in cardiovascular health by modulating lipid metabolism and maintaining vascular integrity. While often considered a female hormone, endogenous estradiol in males—primarily derived from the aromatization of testosterone—is a key regulator of high-density lipoprotein (HDL) levels and endothelial signaling.

Impact on HDL cholesterol

Evidence from large-scale observational studies, including the Multi-Ethnic Study of Atherosclerosis (MESA), consistently demonstrates a positive correlation between estradiol levels and HDL cholesterol in men.

• Hepatic Lipase Suppression: The primary mechanism involves the suppression of hepatic lipase (HL) activity through estrogen receptor (ER) signaling. Lower HL activity prevents the premature hydrolysis of HDL particles, resulting in a higher concentration of larger, more atheroprotective HDL phenotypes.
• ApoA1 Expression: Emerging evidence suggests that estradiol may also upregulate the expression of Apolipoprotein A1 (ApoA1), the foundational protein component of HDL particles.
• Clinical Observations: In studies of healthy men, higher endogenous E2 levels are associated with superior lipid profiles, while the use of aromatase inhibitors—which block the conversion of testosterone to estradiol—frequently leads to a decrease in HDL-C and impaired cholesterol efflux capacity.

Vascular endothelial function

Estradiol supports the inner lining of blood vessels through well-defined molecular pathways that promote vasodilation and protect against atherosclerosis.

• Nitric Oxide Production: Estradiol activates endothelial nitric oxide synthase (eNOS) via non-genomic signaling through estrogen receptor alpha (ERα). This process involves the PI3K-Akt pathway and the recruitment of heat shock protein 90 (Hsp90), which facilitates the release of nitric oxide (NO), a potent vasodilator.
• Protective Signaling: Low levels of estradiol or deficiencies in ERα are associated with reduced flow-mediated dilation (FMD). Mechanistically, the vasodilatory effects of testosterone are partially dependent on its conversion to estradiol to maintain these NO-mediated pathways.

Bottom line

Estradiol is essential for maintaining healthy HDL levels and endothelial signaling in men. Lower levels are associated with reduced HDL particle size and impaired nitric oxide production, potentially increasing the risk for endothelial dysfunction and atherosclerosis.