The thyroid gland makes and releases the thyroid hormone. This hormone is vital to the human body since it has numerous effects. It increases the heat produced by the cells, the heart rate and the speed of muscle contractions. It is essential for the development of the bones and brain. The thyroid hormone also increases the metabolism of carbohydrates, proteins, fats and cholesterol.
What Is Hypothyroidism?
Hypothyroidism is a disorder that can affect someone no matter what her age, but it especially affects the elderly. In people older than 65 years old, almost 10 percent of the women and six percent of the men have this disease, according to Jerome Hershman, M.D., Associate Chief of the Endocrinology and Diabetes Division of the West Los Angeles V.A. Medical Center in "The Merck Manual for Healthcare Professionals." People with hypothyroidism have low levels of the thyroid hormone.
The Causes of Hypothyroidism
Worldwide, the most common cause of this disease is not having enough iodine because the body must have iodine to make the thyroid hormone. In America, Hashimoto's thyroiditis is the main cause of hypothyroidism, per J. Larry Jameson, M.D., Ph.D., Professor of Medicine at Northwestern University Feinberg School of Medicine in "Harrison's Principles of Internal Medicine." Hashimoto's thyroiditis is an autoimmune disease, or a disease where the immune system attacks its own organs instead of what is foreign. In Hashimoto's, the immune system attacks and destroys the thyroid gland.
Features of Hypothyroidism
People with hypothyroidism may have a goiter, or a large thyroid gland. They may be constipated, feel tired and weak, have gained weight and feel depressed. Their skin can be cold, scaly, dry and puffy. They can have carpal tunnel syndrome in their hands and tarsal tunnel syndrome in their feet, which causes tingling and pain. People may have a hoarse voice and speak slowly. Less thyroid hormone makes their heart beat slower, explains Dr. Hershman. Less thyroid hormone will also result in increased cholesterol levels.
Thyroid Hormone and Cholesterol
The thyroid hormone has numerous effects, as described in "Greenspan's Basic & Clinical Endocrinology" by David Cooper, M.D., Director of the Division of Endocrinology at the Sinai Hospital of Baltimore. It is vital for the maturation of the brain and the growth of tissue. It increases the heart rate, heat production, red blood cell production, the movement of the intestines, bone turnover and bone formation. Thyroid hormone also increases the breakdown of fats and cholesterol and the removal of low-density lipoprotein cholesterol.
Thyroid Hormone and LDL Cholesterol
Low-density lipoprotein cholesterol, also referred to as LDL, is the type of cholesterol that has the nickname "bad cholesterol." It has this nickname because high LDL levels are a major risk factor for the development of atherosclerosis in the coronary arteries of the heart, the disease where the arteries get hard and thick. As explained by Dr. Cooper, thyroid hormone increases the removal of LDL and the breakdown of cholesterol. This is why people with hypothyroidism have increased LDL and total cholesterol levels.
References
- "Greenspan's Basic & Clinical Endocrinology"; David Gardner, M.D. and Dolores Shoback, M.D.; 2007
- "Harrison's Principles of Internal Medicine"; Anthony Fauci, M.D., et al.; 2008
- Merck: Hypothyroidism
- University of Maryland Medical Center: Endocrinology Health Guide
