Read an Excerpt
A Simple Guide to Thyroid Disorders
From Diagnosis to Treatment
By Paul Ruggieri, Scott Isaacs, Jack Kusler
Addicus Books, Inc.Copyright © 2004 Paul Ruggieri, M.D. and Scott Isaacs, M.D.
All rights reserved.
Understanding Your Thyroid Gland
If you're like most people, you may not have given much thought to your thyroid gland. Over the years, you've probably heard about other people having thyroid problems; but the truth is that most of know very little about this gland. In fact, we usually don't feel we need to know much about it ... until it causes us a problem. Then, many of us want to gain a better understanding of how this small but powerful gland can have such a dramatic impact on our health.
One in ten Americans is affected by thyroid problems. And unfortunately, as many as half of those people have not been diagnosed. The reasons for the large number of undiagnosed cases include lack of public awareness about thyroid disorders as well as lack of knowledge about the thyroid gland itself. To lay a foundation for a better understanding of thyroid disorders, let's first examine the thyroid gland and its function.
The Thyroid Gland
The thyroid gland is located at the front of your throat, just below your voice box (larynx). It is a light purplish-red, about the size of a hen's egg, weighs less than three-quarters of an ounce, and is encased in a thin layer of tissue.
Shaped like a butterfly, the thyroid has "wings," or rubbery lobes , that are about two to three inches long. The middle section of the so-called butterfly shape is the isthmus.
How the Thyroid Gland Works
A complex organ, the thyroid gland produces hormones that are responsible for keeping virtually every cell and organ in your body functioning normally. You might think of these hormones as a "fuel additive" that makes the "human machine" run smoothly. They help cells convert oxygen and calories into energy.
The thyroid gland works in concert with the hypothalamus and the pituitary gland in the brain to produce thyroid hormones that influence the function of your heart, brain, eyes, skin, muscle, bone, liver, kidneys, and intestines. These hormones also affect growth and development; influence the protein that builds muscle; and are largely responsible for regulating your body temperature, heart rate, mood, alertness, and even the texture and growth of your hair and nails. The functioning of the thyroid gland can also affect weight gain or loss because the gland regulates metabolism, the process by which your body uses up nutrients. The rate at which metabolism occurs is called the basal metabolic rate, or BMR; thyroid hormones help regulate your BMR.
If the thyroid hormones and other chemicals with which they interact get out of balance, a variety of troublesome symptoms can occur. So, take a bit of time and read on to learn about these important chemicals, their functions, and their interdependence with other key organs.
How Thyroid Hormone Is Produced
Chemistry may or may not be one of your favorite subjects, but to gain an understanding of how thyroid hormones can affect your health, it will be helpful if you follow along for a short lesson in chemistry on how your body produces thyroid hormone. Understanding this hormone is the foundation for understanding thyroid disorders. And, t he two hormones that make up thyroid hormone will be referred to by medical professionals repeatedly as you are being tested or treated for a thyroid disorder. So for this reason, having a basic understanding of the chemistry will be helpful to you.
The thyroid gland produces thyroid hormone through a series of chemical interactions. Among these interactions is the absorption of iodine from the bloodstream. Iodine combines with other chemicals to create the hormone thyroxine, also referred to as T4. It's called T4 because it has four atoms of iodine in each molecule. T4 is stored in the thyroid gland attached to the main thyroid protein, thyroglobulin. By itself, T4 is relatively weak and inactive, so to do its work, most T4 is converted into the more active hormone triiodothyronine, known as T3. As you might guess, T3 has three iodine atoms per molecule. These two hormones, thyroxine and triiodothyronine, together make up thyroid hormone.
Now, there is another important aspect to understand about these two hormones, T3 and T4. It relates to whether the hormones are able to do their jobs in helping cells convert oxygen and calories into energy. As these hormones travel through the bloodstream, the vast majority cling to proteins (called thyroid binding globulin or TGB). When the hormones are attached to these proteins, they cannot do their work in helping the body's organs work smoothly. On the other hand, a small amount of thyroid hormone is not stuck to proteins and is floating freely through the bloodstream. Only when the hormone is free can it do its job in keeping the body's metabolism running well.
Accordingly, when doctors talk to you about your thyroid hormone levels, they may speak of the "total" hormone level or the "free" hormone level. The terms are defined as follows:
Total thyroxine (TT4): the body's total amount of thyroxine, most of which is inactive because it is "tied up" with protein.
Free thyroxine (FT4): the active form of the hormone thyroxine, which is not tied to proteins and floats freely in the bloodstream, helping the body's organs work efficiently.
Total triiodothyronine (TT3): the total amount of the body's triiodothyronine, most of which is "tied" to proteins, making it inactive.
Free triiodothyronine (FT3): the active form of the hormone triiodothyronine, which travels freely through the bloodstream, able to do its work.
"Lock and Key" Analogy
If you find the chemistry lesson here a bit confusing, consider an analogy that will add clarity. Think of a locked door and key. The body's organs are the "locks on the door," and the free hormone is the "key." The free hormone can unlock the door, enter the organ, and do its work in making the body function normally. However, because the total hormone is bound up in protein, it is like a key that doesn't fit into the lock. As a result, the hormone cannot do its work.
How the Body Regulates Thyroid Hormone
Like a juggler with fragile balls in the air, your thyroid regulates organs and systems throughout the body by shifting and compensating to maintain a hormonal balance. This balancing act is regulated by a feedback loop system. When too much thyroid hormone is being produced, the brain decreases the secretion of two hormones that slow the production andrelease of thyroid hormone. These hormones are called thyrotropin releasing hormone, or TRH, and thyrotropin or thyroid stimulating hormone (TSH). Similarly, if there is too little thyroid hormone in your blood, the brain knows to increase the production of TRH and TSH.
Thyroid Function at a Glance
Hypothalamus signals the pituitary gland through a hormone, thyrotropin releasing hormone (TRH).
The pituitary releases the thyroid stimulating hormone (TSH)to the thyroid gland.
Upon receiving TSH, the thyroid releases T4, which is converted to "active" T3 in the bloodstream.
The pituitary monitors the levels of thyroid hormone, and increases or decreases the amount of TSH released.
T3 travels through the bloodstream and interacts with organs in the body.
Risk Factors for Thyroid Disorders
Thyroid disease may affect both men and women. However, thyroid disorders are much more common in women. In fact, women are five to eight times more likely to be diagnosed with thyroid disease than men. Approximately one out of eight women will develop a thyroid disorder in her lifetime.
Although thyroid disorders can affect children as well as adults, they are more likely to appear as we get older. By age sixty, nearly 17 percent of women will have an underactive thyroid gland; this group is increasingly susceptible to thyroid disease as their bodies gradually function less efficiently.
It's recommended that all women over the age of forty be tested for thyroid function, since approximately 10 percent of women in this age group are believed to have undiagnosed thyroid disease. Often improperly diagnosed, many women are treated for depression or with estrogen replacement therapy when, in reality, they may need thyroid hormone replacement.
People with a family history of thyroid disease are at a much higher risk of developing one of the disorders than those without a family history. In fact, according to the American Association of Clinical Endocrinologists, 50 percent of those with thyroid disorders will pass thyroid disease on to their children.
In addition, people with a family history of other autoimmune diseases, such as lupus or rheumatoid arthritis, may be at a slightly higher risk to develop thyroid-based autoimmune diseases. Thyroid cancer also may run in families.
A lack of iodine in the diet certainly leads to thyroid disorders. Today, however, iodine deficiency is rarely a problem in the United States. Iodine was added to table salt before the 1920s to counteract a deficiency that had been widespread in the United States. Then, in the 1930s, the government mandated iodization of salt. In the decades following, the use of iodized salt in the United States virtually wiped out endemic goiter, a form of thyroid enlargement caused by a lack of iodine.
Only a trace amount of iodine is needed in the daily diet. Yet without it, the thyroid gland cannot produce thyroid hormone. The food sources with the greatest amount of iodine are saltwater fish and shellfish. Milk, eggs, bread, and meat also provide some iodine. With the exception of spinach, vegetables do not contain much iodine at all.
The body can usually adjust to mild iodine deficiency; the thyroid will enlarge slightly and produce extra hormone. Also, the thyroid can store up to a three-month supply of iodine. But history has shown us that severe iodine deficiency can produce devastating effects on world populations. Populations with iodine deficiencies have experienced high instances of birth defects, mental retardation, speech defects, and stunted growth. Excess iodine can also cause thyroid dysfunction, either overactivity or underactivity. Therefore, iodine supplements (such as kelp) are not recommended.
One clear-cut toxin detrimental to thyroid health is low-level radiation. Children exposed to low-level radiation, whatever the source, are at a much higher risk than the general population to develop thyroid cancer ten to twenty years later in life. The initial exposure can come from living in an area where nuclear testing is being conducted or radioactive waste is stored.CHAPTER 2
Getting a Diagnosis
I didn't realize how much control the thyroid gland has over normal bodily functions until I was diagnosed with a thyroid disorder. I knew something wasn't quite right — I was losing weight and feeling anxious more frequently. I wasn't sleeping well and even had problems with my menstrual cycle. It took almost six months and several blood tests and a thyroid scan to finally get a definite diagnosis of hyperthyroidism.
Thyroid disorders affect more Americans than diabetes and cancer combined. Yet it is estimated that approximately 14 million Americans are unaware that they have a thyroid problem. It is important that thyroid disorders be diagnosed and treated. Otherwise, they can lead to serious health consequences, such as elevated cholesterol levels and heart disease, high blood pressure, osteoporosis, mental illness (including depression), and growth and reproductive abnormalities.
Why is this disorder so frequently underdiagnosed? The early symptoms are usually subtle and can take years to become noticeable. Even when symptoms do start to cause problems, they often mimic those of other diseases or are dismissed as being a result of aging, stress, poor diet, or lack of exercise. Your first line of defense against serious thyroid trouble is your primary care physician, who should have access to your medical history. Every time you go in for a routine physical, he or she can take steps to monitor your thyroid health. If necessary, your primary physician will refer you to a hormone specialist (endocrinologist) for further testing and treatment.
Your personal medical history can alert your doctor to certain risks for thyroid problems. Some thyroid conditions are hereditary. One or both parents through one or more genes pass them on. It's a good idea to learn as much as you can about any thyroid problems in your family and to share this information with your doctor. Particularly relevant is a family history of thyroid cancer or disorders relating to the production of thyroid hormone and the body's ability to use it efficiently.
Finally, if you have ever received radiation treatments to the neck area, or if you have ever lived in parts of the country where above-ground nuclear tests were conducted, you probably have a higher-than-average risk for hypothyroidism, thyroid nodules, or even thyroid cancer. If your doctor knows about such exposure, he or she will be on the lookout for early symptoms.
Be sure that your doctor is aware of any medications you take routinely. Some can interfere with normal thyroid function. These include, for example, lithium (Lithobid, Eskalith), amiodarone (Cordarone), and interferon medications (Intron A, Rebetron, Infergen, Avonex, and Betaseron. Over-the-counter supplements that contain high amounts of iodine, such as kelp, frequently disrupt normal thyroid function. Estrogen containing medications, such as birth control pills and hormone replacement therapy, can affect some types of thyroid hormone testing without actually causing a thyroid problem. It is important to inform your doctor if you are taking these medications so that he or she can order the appropriate thyroid tests.
Once your doctor has talked with you about your medical history and any symptoms that trouble you, he or she will examine you for visible signs of thyroid problems. During the physical part of your checkup, he or she will also feel, or palpate, your thyroid gland manually. You will be asked to swallow, which will cause your thyroid to move up and down. Feeling your thyroid as it moves gives your doctor a good idea of its shape and size, indicating whether it is enlarged or has developed any growths, or nodules.
During a physical exam, it is important to mention symptoms or bodily changes to your physician. Don't dismiss even vague feelings that something might be wrong. For example, general complaints such as frequent tiredness or nervousness or an increased sensitivity to cold could signal thyroid problems. Tell your doctor as well about any eye problems, gradual weight changes, persistent constipation, menstrual problems, difficulty sleeping, dry skin, hair loss, heart palpitations, difficulty swallowing, or gradual hoarseness.
Thyroid Neck Check
The American Association of Clinical Endocrinologists recommends this self-exam to help determine whether you have an enlarged thyroid gland or thyroid nodule, which may need further examination and testing by an endocrinologist.
1. Hold a mirror in your hand, focusing on the area of your neck just below the Adam's apple and immediately above the collarbone. Your thyroid gland is located in this area of your neck.
2. While focusing on this area in the mirror, tip your head back.
3. Take a drink of water and swallow.
4. As you swallow, look at your neck. Check for any bulges or a protrusion in this area when you swallow. Reminder: Don't confuse the Adam's apple with the thyroid gland. The thyroid gland is located further down on your neck, closer to the collarbone. You may want to repeat this process several times.
5. If you do see any bulges or protrusions in this area, see your physician immediately. You may have an enlarged thyroid gland or a thyroid nodule and should be checked to determine whether cancer is present or if treatment for thyroid disease is needed.
Excerpted from A Simple Guide to Thyroid Disorders by Paul Ruggieri, Scott Isaacs, Jack Kusler. Copyright © 2004 Paul Ruggieri, M.D. and Scott Isaacs, M.D.. Excerpted by permission of Addicus Books, Inc..
All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.
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