Testosterone levels peak in men during early adulthood and gradually decline after age 30. Research has long indicated that normal testosterone levels (250 to 850 ng/dl, depending on age) are necessary to maintain heart health. Levels that are too high or too low have a correlation to heart disease.

One way testosterone works in conjunction with the heart is by increasing artery diameter so that blood can flow more freely. This helps relieve angina in men with coronary artery disease.

Recent studies have confirmed the importance of testosterone for heart health:

• In England, researchers looked at 930 men who already had been diagnosed with heart disease. After seven years, one in five men with low testosterone died, compared to just one in eight of the men with normal testosterone levels.

• A team of medical researchers reviewed Pub Med articles from 1980 through 2008 concerning testosterone deficiency and heart disease. They found that men with low testosterone had higher cholesterol, higher LDL cholesterol, higher inflammation, and increased thickness of artery walls — all factors that increase the risk of heart disease.

• A National Institutes of Health study followed 697 men over the age of 65 for four years. All of the men had blood tests to determine their testosterone levels, and none were taking any testosterone supplements. At the end of the study, 14 percent had suffered a heart attack or coronary event. Those with the highest levels of testosterone had twice the risk of heart disease as those with the lowest testosterone.

In women, a high testosterone level poses greater risk of heart disease. A study of 344 women age 65 to 98 showed that women with the highest testosterone levels — those in the top 25 percent of the study group — had three times the risk of heart disease as women with lower levels.

However, in older women with very low testosterone, a low dose of the hormone seems to aid against heart failure. One study tested a testosterone patch against a placebo. After six months, the testosterone group had improved muscle strength and better tolerance for exercise, factors that are important when living with congestive heart failure.

A similar study found that one in four men with heart failure have low testosterone. When testosterone injections were given, the heart gained strength and was better able to pump blood.

Testosterone supplementation should be monitored by a physician. Any history of cancer or prostate enlargement must be considered before embarking on hormone treatment.