Low Thyroid Increases Heart Risk

Hypothyroidism Relationship to Heart Disease and Cardiac Problems


"Older women with subclinical hypothyroidism were almost twice as likely as women without this condition to have blockages in the aorta. They were also twice as likely to have had heart attacks."

According to research published in the Annals of Internal Medicine, a slightly underactive thyroid -- the condition known as subclinical hypothyroidism -- is a major heart disease risk for older women. In the Dutch study, which is being called "The Rotterdam Study," it was found that older women with subclinical hypothyroidism were almost twice as likely as women without this condition to have blockages in the aorta. They were also twice as likely to have had heart attacks.

This common condition, which frequently has no obvious symptoms for patients, and no observable symptoms for doctors, is a strong risk factor for both hardening of the arteries and heart attacks in older women.

Subclinical hypothyroidism is detectable by a blood test, known as the Thyroid Stimulating Hormone (TSH) test. For the purposes of this study, subclinical hypothyroidism was defined as a TSH level greater than 4.0 mU/L in the presence of a normal free thyroxine (Free T4) level. Clinical hypothyroidism was defined as a TSH level greater than 4.0 mU/L and a decreased free thyroxine level.

The Rotterdam Study's finding is a strong indication that screening programs to evaluate even slight hypothyroidism in older women could help prevent cardiovascular illness.

The thyroid is a butterfly-shaped gland that wraps around the windpipe, behind the "Adam's Apple" area of the neck. The hormones produced by the gland are essential to stimulating metabolism, growth, and the body's capacity to process calories. An underactive thyroid -- hypothyroidism -- is estimated to affect as many as 10 to 20 percent of women in their lifetimes, and is more common in women than men. The symptoms of hypothyroidism include fatigue, depression, weight gain, hair loss, muscle and joint pains, and many other chronic and debilitating symptoms. Low thyroid can also be linked to increased levels of LDL -- "bad" cholesterol -- and heart disease.

In the study, even after statistically adjusting for all the other factors affecting heart disease risk - - including weight, smoking, cholesterol levels, and blood pressure -- women with hypothyroidism were 70 percent more likely to have hardened aortas -- the body's main artery -- than those with normal hormone activity.

They also had more than twice the risk of heart attack. Having autoimmune hypothyroidism increased the risk even further.

According to Dr. Paul Ladenson, a thyroid specialist at Johns Hopkins University, hypothyroidism may be more common than currently thought. Ladenson's own studies indicate that as many as 17 percent of older American women in the United States may have the condition.

Lower Newton Falls, Massachusetts endocrinologist Kenneth Blanchard, M.D. feels that number may actually be higher, and that hypothyroidism is underdiagnosed in the population. In my book, Living Well With Hypothyroidism: What Your Doctor Doesn't Tell You. . . That You Need to Know, Dr. Blanchard says the normal ranges of the tests may be too wide and people at the end of the ranges are excluded from valid diagnoses. Says Blanchard:

"The key thing is of course that what doctors are always told is that TSH is the test that gives us a yes or no answer. And, in fact, I think that's fundamentally wrong. The pituitary TSH is controlled not just by how much T4 and T3 is in circulation, but T4 is getting converted to T3 at the pituitary level. Excess T3 generated at the pituitary level can falsely suppress TSH.

In his book, The Thyroid Solution, Ridha Arem, MD, Associate Professor of Medicine in the Division of Endocrinology and Metabolism at Baylor College of Medicine, also agrees that hypothyroidism may exist despite "normal range," TSH levels:

Many people may be suffering from minute imbalances that have not yet resulted in abnormal blood tests. If we included people with low-grade hypothyroidism whose blood tests are normal, the frequency of hypothyroidism would no doubt exceed 10 percent of the population. What is of special concern, though, is that many people whose test results are dismissed as normal could continue to have symptoms of an underactive thyroid. Their moods, emotions, and overall well-being are affected by this imbalance, yet they are not receiving the care they need to get to the root of their problems....Even if the TSH level is in the lower segment of the normal range, a person may still be suffering from low-grade hypothyroidism...

What's clear is that serious consideration should be given to instituting hypothyroidism screening for all older women, and that efforts should be made to determine the optimal TSH ranges at which the risks of complications such as heart disease or hardening of the arteries is reduced.