Changes in blood vessel chemistry may explain why estrogen changes from a heart protector to a heart danger as women age. Before menopause, estrogen functions as a dilator of blood vessels, offering a protective effect to the heart. However, later in life estrogen's function changes to a constrictor of blood vessels, which could be dangerous.

Researchers hope their further understanding of estrogen's role in the body will help to make hormone replacement therapy (HRT) safer. A 15-year study of more than 161,000 women found that HRT, though promoted to reduce the risk of heart attack and stroke in postmenopausal women, actually increases the risk. Doctors were left puzzled at the conflicting findings.

Researchers began studying the effect of estrogen on blood vessels and found that estrogen targets the enzyme nitric oxide synthase 1, which makes the vasodilator, nitric oxide. They tried to block estrogen's activity by blocking nitric oxide, and found that, surprisingly, the estrogen had changed into a constrictor agent, one that would increase blood pressure.

Further, it was found that aging naturally decreases levels of the cofactors L-arginine and tetrahydrobiopterin, which are both necessary to nitric oxide synthase's production of nitric oxide. Rather than making nitric oxide, the estrogen was making an age-promoting and vasoconstricting oxygen free radical, superoxide.

Superoxide is an oxidant that causes cellular damage and, researchers found, constriction. They noted that estrogen is a powerful agent--one that can affect every bodily system. As cofactors drop that enable estrogen to relax blood vessels, the researchers question what effects it will have on blood pressure, Alzheimer's and other systems in the body.

Medical College of Georgia February 16, 2005

Dr. Mercola's Comments:

Although there is plenty of evidence synthetic hormone replacement therapy (HRT) can affect women in serious, harmful ways, little is known about why estrogen use can be so risky. This study has helped to shed some light on that issue. Synthetic progestins like Provera are the stealth element of conventional estrogen replacement therapy (ERT) and are responsible for nearly all the side effects. They should rarely be used by any woman. The most popular estrogen women use--Premarin--comes from horse estrogens and is also best avoided. It is far better to use genuine human hormones that are easily available through any compounding pharmacist. When it comes to estrogen, many experts believe all most women need is estradiol, which is bioidentical to the primary human female hormone. Unfortunately there is still much unnecessary concern about bioidentical estradiol supplementation. What the FDA and most doctors and patients do not realize is that bioidentical hormone supplements can actually optimize your health. Ideally, these levels should be monitored by either urine or blood levels so they reach a target level that correspond to the reference ranges for healthy young women. Other tools you can use to help you optimize your hormone levels include: Adopting a better diet based on your personal nutritional type Balancing your omega-3 and omega-6 fat intake Starting an exercise program, even of the low- to moderate-intensity variety Eliminating grains (unless you are normal body weight) and sugars as they cause yeast overgrowth that worsen hormone levels Eliminating caffeine and alcohol as it can also have adverse effects on hormone levels Related Articles: Estrogen Replacement Can Be Healthy or Dangerous Odds Are Even You'll Have Osteoporosis By 2020 Endometriosis and Women's Health Hormone Replacement Therapy Reverses Effects of Aging Delay the Aging Process Naturally Avoiding Osteoporosis Can Start Before Puberty