Don’t Overlook Thyroid in War on Cholesterol
If you’re among the 35 million Americans with elevated cholesterol levels, ask your doctor about getting tested for thyroid disease. Estimates are that up to 14% of people with elevated cholesterol may also have an underactive thyroid--and that treatment of the thyroid condition can help reduce cholesterol levels.
“People who have a total cholesterol level of 240 or more should have a thyroid test done before they start any diet or drug therapy,” said Peter Kwiterovich, chief of the lipid research atherosclerosis program at Johns Hopkins Medical Institutions in Baltimore. Having too little thyroid hormone can contribute to cholesterol problems, complications and treatment, Kwiterovich says.
None of this means that genes and diet--long associated with heart disease--are less important. Along with being overweight, eating a high-fat, high-cholesterol diet and having a family history of cholesterol problems remain the leading risk factors for developing high blood cholesterol levels and related risks of heart disease. But growing scientific evidence points to thyroid deficiency as a contributor to elevated cholesterol and other health problems.
“The message here is that hypothyroidism (thyroid deficiency) can also be a common cause of high blood cholesterol levels,” said Paul Ladenson, director of the division of endocrinology and metabolism at Johns Hopkins. The thyroid condition should be diagnosed, he said, “because reversing it can either completely correct the high cholesterol or make it easier to treat with other measures.”
Tucked below the Adam’s apple in the neck, the thyroid is a small, butterfly-shaped gland that regulates metabolism by releasing hormones. The brain communicates with the thyroid by sending chemical messages transmitted via the pituitary gland, which acts as a kind of thermostat, turning thyroid production up and down as needed. To complete the loop, circulating thyroid hormones signal the brain to boost or drop thyroid production.
For about 3% of people with elevated blood cholesterol levels, thyroid deficiency is the sole problem, according to Kwiterovich. Once the deficiency is diagnosed and treated, blood cholesterol levels quickly return to normal. Detection occurs with a simple blood test that costs about $25. Treatment consists of daily replacement with thyroid hormone--thyroxin--given in a tiny pill that costs less than 50 cents per day. Hypothyroidism is far more common among women than men.
Doctors are also coming to appreciate--especially with regard to the cholesterol connection--the damage from a less-severe form of hypothyroidism. Often called “subclinical” because it produces no real symptoms, this type of thyroid deficiency occurs in about 10% of women, several studies have suggested. Not only does it complicate treatment of elevated blood cholesterol levels, but it may also increase the risk of heart disease.
The latest evidence about subclinical hypothyroidism comes from a Dutch study of elderly women published last week in the Annals of Internal Medicine. Researchers from Erasmus University Medical School in Rotterdam found that women with low levels of thyroid hormone were twice as likely to have clogged arteries and to have suffered a heart attack as women with normal levels.
“I was kind of awestruck that hypothyroidism could have such a strong effect,” said Ladenson. “It’s time to throw out the word ‘subclinical’ especially in light of this new evidence that there are clinical consequences associated with this mild thyroid deficiency.”
Thyroid function appears to affect heart-disease risk in multiple ways. In the liver, thyroid hormone determines how well the most harmful form of cholesterol--low-density lipoprotein (LDL)--is removed from the blood by increasing the number of LDL receptors in the liver.
Thyroid deficiency can also selectively increase diastolic blood pressure (the pressure on vessels when the heart rests between beats), increase blood-clot formation and elevate other substances, including homocysteine, that increase heart-disease risk. It can also cause complications for those taking cholesterol-lowering medications.
The good news is that detection and treatment of thyroid deficiency can significantly lower health risks. “I have seen women and men who had hypothyroidism and a blood cholesterol level of 230 that went down to 200 just with treatment of their thyroid problem,” said Margo Denke, a Dallas cardiologist and a member of the National Cholesterol Education Program’s Adult Treatment Panel.
The problem is that screening for thyroid problems is still spotty at best, even among high-risk groups. A recent survey by the American Assn. of Clinical Endocrinologists found that more than half of people with elevated blood cholesterol had not had their thyroid levels checked. “That’s a big problem,” said the association’s president, Richard A. Dickey.
For this reason, the association is urging consumers with elevated blood cholesterol levels to ask their physicians about thyroid testing.
“If they have an underlying thyroid condition in addition to their high cholesterol,” Dickey said, “the cholesterol problem will be difficult to control until normal levels of thyroid hormone are restored.”
