Atherosclerosis and Cardiovascular Disease
Hormones and Cardiovascular Health
Testosterone and Estrogen Balance (Men)
Recent studies suggest that testosterone-replacement may improve the symptoms of vascular disease. A placebo-controlled crossover study in men with ischemic heart disease and low testosterone levels reported that exercise time and the time to development of ischemic changes on a treadmill test were both increased with testosterone-replacement therapy (Malkin, 2004).
It has been shown that men with lower levels of testosterone have poorer endothelial function. In a study of 187 males, researchers found that those men in the highest quartile of testosterone levels had 1.7 fold greater flow mediated dilation, a marker of endothelial function (Akishita, 2007).
In another study, researchers examined the correlation between testosterone levels and mortality in over 900 men with coronary heart disease. The team found that the mortality rate in patients with testosterone deficiency was 21%, while only 12% of subjects with normal testosterone levels died. The authors of the study concluded that "in patients with coronary disease testosterone deficiency is common and impacts significantly negatively on survival" (Malkin, 2010).
Researchers analyzed 30-day survival data for 126 men who had suffered a heart attack. All of the men who did not survive were found to have low total testosterone levels (<= 300 ng/dL). The team went on to conclude that "a low level of testosterone was independently related to total short-term [post-heart attack] mortality (Militaru, 2010).
Testosterone levels are also inversely associated with the development of coronary artery disease. In a study of men 45 years of age or younger, researchers found that subjects with diagnosed coronary artery disease had significantly lower levels of free testosterone than did healthy, age-matched controls. The researchers went on to caution that, based on their findings, "a low level of free testosterone may be related to the development of premature coronary artery disease" (Turhan, 2007).
Italian researchers compared plasma testosterone levels of 119 elderly men with isolated systolic hypertension to those of 106 nonhypertensive elderly men. All the study participants were 60 to 79 years old, non-obese, nondiabetic, and nonsmokers. The hypertensive men were found to have 14% lower levels of testosterone compared to the nonhypertensive men. In both the hypertensive and nonhypertensive men, low testosterone levels correlated with higher blood pressure values (Fogari, 2003).
In a study of over 11,000 men, followed for up to 10 years, baseline testosterone concentrations were inversely associated with cardiovascular and all-cause mortality. Men with total testosterone levels of 481 ng/dL or greater at baseline were significantly less likely to die of cardiovascular disease or any cause during the follow-up period compared to men with testosterone levels below 481 ng/dL. The correlation held even after adjustment for various other confounding factors. The authors of this study declared that "low testosterone may be a predictive marker for those at high risk of cardiovascular disease" (Khaw, 2007).
A study published in the Journal of the American Medical Association (JAMA) measured blood estradiol (a dominant estrogen) in 501 men with chronic heart failure. Compared to men in the balanced estrogen quintile, men in the lowest estradiol quintile were 317% more likely to die during a 3-year follow-up, while men in the highest estradiol quintile were 133% more likely to die (Jankowska, 2009).
The men in the balanced quintile—with the fewest deaths—had serum estradiol levels between 21.80 and 30.11 pg/mL. This is very similar to the optimal range that Life Extension has long recommended for aging men. The men in the highest quintile who suffered 133% increased death rates had serum estradiol levels of 37.40 pg/mL or above. The lowest estradiol group that suffered a 317% increased death rate had serum estradiol levels under 12.90 pg/mL.
For more information on optimizing male hormone levels in order to prevent not only vascular disease, but many other age-related diseases as well, please review the chapter on Male Hormone Restoration Therapy.
Testosterone Protects Women Too
Testosterone is often thought to be beneficial only for men. However, a study of nearly 3,000 women reveals that maintaining optimal testosterone levels is important for females as well. After assessing testosterone levels at baseline, researchers found that, over a 4.5 year follow-up period, those women with the lowest levels of testosterone were more likely to experience a cardiovascular event and to die of any cause than women with the highest testosterone. The authors concluded "low baseline testosterone in women is associated with increased all-cause mortality and incident cardiovascular events independent of traditional risk factors" (Sievers, 2010).
DHEA (Men and Women)
DHEA is a precursor to sex hormones such as testosterone and estrogen. Levels of steroid hormones, including DHEA, decline with the age-associated onset of a variety of medical conditions, including chronic inflammation, hypertension, and atherosclerosis. Higher levels of DHEA in humans are associated with lower levels of inflammatory biomarkers (Sondergaard HP et al 2004).
A study showed that men with high levels of DHEA tended to have greater protection against aortic atherosclerosis progression (Hak AE et al 2002). Similarly, another study of 419 Japanese individuals found that those with the highest circulating levels of DHEA-sulfate (form of DHEA commonly measured on blood tests) were much less likely to have carotid atherosclerosis (Yoshida, 2010).
Animal studies show a protective role for DHEA in preventing atherosclerosis. Providing DHEA to human vascular endothelial cells in culture increases nitric oxide synthesis, which boosts blood flow (Simoncini T et al 2003).
Several studies have determined that non-bioidentical progestin promotes the formation of atherosclerosis (Register, 1998; Levine, 1996). The story is quite different for bioidentical progesterone, where multiple animal studies have shown that bioidentical progesterone inhibits the process of atherosclerosis (Morey, 1997; Houser, 2000). To illustrate, scientists fed postmenopausal monkeys a diet which is known to cause atherosclerosis for 30 months. The scientists then divided the monkeys into groups that received estrogen alone, estrogen plus non-bioidentical progestin, or a control group that did not receive hormones. The control group developed substantial atherosclerotic plaque. The administration of estrogen resulted in a 72% decrease in atherosclerotic plaque, compared to the control group. Treatment with non-bioidentical progestin yielded disturbing results. The group that received estrogen combined with non-bioidentical progestin had a similar amount of atherosclerotic plaque as the control group, meaning that non-bioidentical progestin completely reversed estrogen's inhibitory effects on the formation of atherosclerosis (Adams, 1997). In contrast, when the same investigators administered bioidentical progesterone along with estrogen, no such inhibition of estrogen's cardiovascular benefit was seen (Adams, 1990).
In a trial published in the Journal of the American College of Cardiology, researchers studied postmenopausal women with a history of heart attack or coronary artery disease. The women were given estrogen in combination with either bioidentical progesterone or non-bioidentical progestin. After 10 days of treatment the women underwent exercise treadmill tests. Compared to the non-bioidentical progestin group, the amount of time it took to produce myocardial ischemia (reduced blood flow to the heart) on the exercise treadmill was substantially improved in the bioidentical progesterone group (Rosano, 2000).
Growing evidence suggests that estriol may offer benefits to the cardiovascular system. For instance, Japanese scientists found that a group of menopausal women given estriol for 12 months had a significant decrease in both systolic and diastolic blood pressure (Takahashi, 2000). Another study compared the use of estriol for 10 months in 20 postmenopausal and 29 elderly women. Some of the elderly women had decreases in total cholesterol and triglycerides and an increase in beneficial HDL (Nishibe, 1996).
To examine the effects of estriol on atherosclerosis, researchers conducted an experiment in which female rabbits were fed a high cholesterol diet with or without supplemental estriol. The rabbits had their ovaries removed surgically to mimic menopause. Remarkably, the group receiving estriol had 75% less atherosclerosis than the group fed the high cholesterol diet alone (without estriol) (Kano, 2002).
Following menopause, circulating levels of estrogen are depleted. Phytoestrogens are plant hormones with estrogenic activity. In postmenopausal women, phytoestrogens appear to have estrogen-like benefits such as protection against osteoporosis (Atkinson C et al 2004; Crisafulli A et al 2004a) and possibly hot flashes (Crisafulli A et al 2004b). Phytoestrogens have also been shown to improve vascular function, which tends to decline with age. In one study genistein, a phytoestrogen, provided in a daily 54 mg supplement for one year, significantly improved endothelium-dependent vasodilation in postmenopausal women. Moreover, its benefits were as substantial as those observed in women receiving an estrogen-progestin regimen (Squadrito F et al 2003).
For more information on optimizing female hormone levels in order to prevent not only cardiovascular disease, but other age-related diseases as well, please review the chapter on Female Hormone Restoration Therapy.