SUNDAY, Jan. 16 (HealthDayNews) -- High cholesterol is a well-known health problem among Americans, particularly those at risk for stroke or heart disease.
By comparison, thyroid disease is a relatively obscure ailment, with many people unable to say where the gland is and what it does.
What many people also don't know is that a malfunctioning thyroid gland can cause high and potentially deadly levels of cholesterol in the blood.
An estimated 27 million Americans have an overactive or underactive thyroid gland, but more than half remain undiagnosed, according to the American Association of Clinical Endocrinologists.
The thyroid gland is located in the middle of the lower neck, below the voice box and just above your collarbone. It is shaped like a bow tie, with two halves called "lobes" connected by an "isthmus" in the middle, according to the American Academy of Otolaryngology -- Head and Neck Surgery.
"The thyroid gland regulates the metabolic functions of the body in virtually every cell," said Dr. Carlos Hamilton, president of the American Association of Clinical Endocrinologists. "Everything from the brain to the skin is affected by the hormone made by the thyroid gland."
And if the gland goes haywire, or comes under attack from disease, the consequences can be serious.
January is Thyroid Awareness Month, and endocrinologists and other clinicians are using the occasion to educate people about the risks posed by thyroid disease.
If the thyroid gland is producing too little thyroid hormone -- a condition called hypothyroidism -- the body's metabolism starts to slow down.
That can lead to high cholesterol levels in the blood, as the lack of thyroid hormone slows the liver's ability to process blood, said Dr. Paul Jellinger, president of the American College of Endocrinology.
"The sponge-like activity of the liver to soak up excess cholesterol from the blood doesn't work as well as it should with low levels of thyroid," Jellinger said.
This causes an increased risk of cholesterol build-up in the arteries and around the heart, increasing the risk for heart disease.
Hypothyroidism is the most common secondary cause of high cholesterol after diet, according to the National Cholesterol Education Program.
Ninety percent of patients with hypothyroidism have increased cholesterol, and the average blood cholesterol levels of patients with an underactive thyroid are often 30 percent to 50 percent higher than desirable.
Hypothyroidism also has other effects. "It slows you down," Hamilton said. "It makes you lethargic and fatigued." Your hair becomes brittle, and your skin becomes dry. You become cold much easier than the average person.
"Everything's running on a lower gear," Jellinger said. "It's like an eight-cylinder engine running on four cylinders."
Women are far more likely to have thyroid disease. More than eight out of 10 patients with the condition are women.
Pregnant women and the elderly are particularly affected by hypothyroidism.
Nearly one of 50 women in the United States is diagnosed with hypothyroidism during pregnancy, and 5 percent to 17 percent of women are diagnosed with the condition postpartum.
The incidence of hypothyroidism also increases with age. By 60, as many as 17 percent of women and 9 percent of men have an underactive thyroid.
The good news is that high cholesterol caused by hypothyroidism is highly treatable, Jellinger said. Much of the time, thyroid patients can avoid using cholesterol-lowering drugs simply by treating their condition.
"As the thyroid abnormality becomes more intense, the ability to lower cholesterol is very striking," Jellinger said. "Often the only treatment needed to lower cholesterol is thyroid medication."
People with an overactive thyroid gland, or hyperthyroidism, also must be concerned about cholesterol.
Their condition causes a high metabolic rate that can artificially lower cholesterol levels, Jellinger said. People being treated for hyperthyroidism must watch their cholesterol levels as their metabolism returns to a normal level.
Both hyperthyroidism and hypothyroidism are easily treated through medication, said Dr. Bill Law, an endocrinologist in Knoxville, Tenn.
"One little pill a day, very inexpensive, and no side effects," Law said. "If you have to have a disease, it's a good one in terms of treatment."
The bad news is the disease is genetically influenced more than anything else, meaning there's little you can do to prevent its onset.
"Other than maintaining good nutrition, there isn't really much a person does that affects their thyroid gland," Hamilton said.
The diseases are diagnosed through a simple blood test that family physicians can perform in their office.
For more on thyroid disorders, visit the National Library of Medicine.