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Low Thyroid Function without Symptoms as a Risk Indicator for Heart Disease in Older Women
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What is the problem and what is known about it so far?
Hypothyroidism is a condition in which the thyroid, a gland located in the neck, makes too little thyroid hormone. Thyroid hormone is important in regulating the body's use of energy, fats, and protein. The symptoms of hypothyroidism include tiredness, intolerance to cold, muscle aches and stiffness, dry skin, and constipation. It is well known that if people with hypothyroidism severe enough to cause symptoms and abnormal thyroid laboratory tests are not treated, their risk for heart disease increases. However, many older persons who have no symptoms have thyroid tests that suggest a milder degree of hypothyroidism (sometimes called subclinical hypothyroidism).
Why did the researchers do this particular study?
The researchers wanted to find out if subclinical hypothyroidism also puts people at risk for heart disease.
Who was studied?
1149 women participating in a large study of chronic disease in older persons in Rotterdam, the Netherlands. All of the women in the study had been through menopause.
How was the study done?
Between 1990 and 1993, the researchers evaluated women in the study to see if they had blockages in their aorta (a large blood vessel leading from the heart to the body) or any evidence of a past heart attack. At the same time, the researchers collected blood tests of thyroid function.
What did the researchers find?
Almost 11% of the women had subclinical hypothyroidism at the beginning of the study. 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.
What were the limitations of the study?
Both information on thyroid function and information on heart and aorta disease were collected at the same time. Therefore, we cannot be sure that the subclinical hypothyroidism caused the disease.
What are the implications of the study?
In older women, low thyroid function even in the absence of symptoms (subclinical hypothyroidism) appears to increase the risk for heart and blood vessel disease.
Article and Author Information
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The summary below is from the full report titled “Subclinical Hypothyroidism Is an Independent Risk Factor for Atherosclerosis and Myocardial Infarction in Elderly Women: The Rotterdam Study.” It is in the 15 February 2000 issue of Annals of Internal Medicine (volume 132, pages 270-278). The authors are A.E. Hak, H.A.P. Pols, T.J. Visser, H.A. Drexhage, A. Hofman, and J.C.M. Witteman.
- Copyright ©2004 by the American College of Physicians
