For such a small gland, the thyroid in the neck can cause a lot of problems. That's because the thyroid gland releases hormones that affect almost all of your body's functions. As a result, thyroid disease produces such a wide range of symptoms, from weight gain to high cholesterol to infertility.
The most common thyroid diseases occur when the thyroid gland releases either too little or too much thyroid hormone.
Even though a simple test can be given to figure out how much thyroid hormone you are producing, many people do not realize that their thyroid gland is responsible for symptoms such as fatigue, if they have an underactive thyroid, or a rapid heartbeat, if they have an overactive thyroid.
Some people may even have subclinical thyroid disease, where they have subtle symptoms that are very rarely properly diagnosed.
Below, Carlos R. Hamilton, Jr., MD, president of the American Association of Clinical Endocrinologists and the executive vice president of the University of Texas Health Science Center at Houston, discusses the diagnosis and treatment of thyroid disease.
What does the thyroid hormone do in the body?
The thyroid hormone is necessary for almost all of the body's chemical processes to proceed the way they are supposed to. The body needs it to allow cells to consume oxygen and generate energy within the cells. The cells are continually regenerating, making new proteins, storing glucose, making new enzymes and synthesizing DNA. When there is too little or much thyroid hormone, these processes don't proceed properly. Almost any tissue in the body is affected by the thyroid gland and by thyroid hormone.
Tissues that tend to use more oxygen tend to be affected more, so the central nervous system, the heart, the bones, the skin and the muscles are all very significantly affected by either too much or too little thyroid hormone. When thyroid hormone is not present, the skin, for example, is not able to replace itself, and it becomes thin. With too much thyroid hormone, you might break down proteins too quickly,causing muscle weakness.
What is hyperthyroidism and hypothyroidism?
Hypothyroidism means there is not enough thyroid hormone in one's system. Hyperthyroidism is just the opposite; it means that there is too much. Hashimoto's disease may cause the thyroid gland to become underactive or enlarged over time. Treatments for hyperthyroidism with radioactive iodine, radiation therapy for head and neck cancers, and thyroid surgery, as well as certain medications can also cause hypothyroidism. Grave's disease is the common cause of hyperthyroidism, though it may also be caused by thyroid nodules and thyroid inflammation.
Who are these conditions most likely to affect?
Thyroid diseases, in general, are more common in women than they are in men. They are more common right after pregnancy. They are more common in older people. Equally important is one's family history. If people in your family have an overactive or an underactive thyroid, then you would be considered at higher risk. So, knowing if your family members have had thyroid disease and making sure your doctor knows that is very helpful.
What are some of the major symptoms of an overactive thyroid gland?
Hyperthyroidism tends to stimulate the system in a number of ways: it causes rapid heartbeat, tremor of the hands, sweatiness of the skin and anxiety. Too much thyroid hormone can make the muscles weak, and, over a longer period of time, it can affect the bones and increase one's likelihood of developing osteoporosis. Too much thyroid hormone also affects hormonal status in terms of the menstrual cycle and the ability to bear children. It leads to less frequent menstrual periods, and it decreases the likelihood of being able to get pregnant.
What are the major symptoms of an underactive thyroid gland?
The principle symptom of hypothyroidism is fatigue, or lethargy, and a slowing down of one's mental processes. It affects people's mental alertness and their general strength and stamina. It also generally causes rougher, dry and thickened skin and dry hair. People with an underactive thyroid, oftentimes, will have high cholesterol levels. It can also cause depression and weight gain.
How are these conditions diagnosed?
Before you can diagnose these conditions, you have to suspect them. These symptoms are rather nonspecific, so it is a very good idea for the physician to test the thyroid, and that is very easily done by a simple blood test called the TSH test. TSH stands for thyroid-stimulating hormone, and it is a hormone produced by the pituitary gland. It is the hormone that regulates the amount of thyroid activity, so when your thyroid blood levels go down, the TSH goes up. And when the TSH goes up, it stimulates the thyroid gland to make more thyroid hormone. It's kind of like your thermostat for thyroid hormone. A normal TSH is generally between 0.5 and 3.5.
When I highly suspect someone has a thyroid problem, I might do a TSH test and a test to measure blood levels of the thyroid hormone with a T3 (triiodothyronine) and a T4 (thyroxine) test. T3 and T4 are two different types of thyroid hormone that the thyroid gland releases. I also do a physical exam and a thyroid scan or ultrasound to look for lumps or cysts on the gland. Some nodules may be producing too much thyroid hormone, and some might need to be biopsied to see if they are cancerous or benign.
How is hypothyroidism treated?
If the thyroid gland is underactive, then it is very easy to treat. Hypothyroidism is treated by giving a person additional thyroid hormone. A simple tablet taken just once a day, can bring the thyroid level up to normal so that the TSH comes down to normal.
One of the interesting things is that thyroid hormone medication made by different companies or from different sources is absorbed differently by different patients, so that if you change from one thyroid hormone to another, you may actually either become hypothyroid, even though you think you're taking the same dose. So it is important to stay on the same thyroid hormone and then to have your TSH monitored periodically to make sure that the same dose is still the best dose for you.
Also, as we get older and our situations change and sometimes the amount of thyroid hormone is a little bit different, so you need to make sure that the dosage is exactly right for that person.
How is hyperthyroidism treated?
Hyperthyroidism, an overactive thyroid gland, can be treated in different ways. We can use drugs that block the effect of thyroid hormone, such as propylthiouracil (PTU) and Tapazole. And sometimes we use radioactive iodine that shrinks the cells in the thyroid to keep them from functioning as actively as before. Sometimes you can treat hyperthyroidism with surgery by removing most of the thyroid gland.
What is subclinical hyperthyroidism or hypothyroidism?
Subclinical hyperthyroidism and subclinical hypothyroidism are conditions that we use to refer to a situation where a person's TSH level is abnormal, but the blood levels of the thyroid hormone may be within the normal range. The normal blood level of thyroid hormone range is anything from 4.5 to 10.5. The TSH test is more sensitive than the test measuring the blood level of thyroid hormone. For example, a level of 9 might be normal for you, and if goes down to 5, your TSH will then go up. That would tell us that a blood thyroid hormone number of 5 is too low for you.
Subclinical disease is a very important situation that physicians discuss because the presence of thyroid disease as it comes on a person, whether it's underactive or overactive, isn't something that just comes on overnight like the measles. This is something that gradually develops, in most cases, over a period of weeks or months and sometimes years. So there is a point at which a person has something wrong with their thyroid gland, but it may be so mild that some of the tests might not show that it's present.
Do people with these subclinical conditions have symptoms?
Some do, but many of these patients don't say they have any symptoms at all. They don't feel fatigue, they're not aware of weakness, they're not aware of their heart beating unusually, they're not aware of any changes in their skin. But if some of these people do have subclinical hypothyroidism, for example, and you treat them with a small amount of thyroid hormone and their TSH becomes normal and they come back to see you, they will say, "You know, I really do feel a lot better. I didn't realize that I was fatigued or that my skin was dry. And now that I'm on this medication, I feel a lot better."
What is your advice to people who have symptoms that indicate they may have a thyroid problem?
If a person has a symptom that they think might be due to the thyroid abnormality, whether too much or too little thyroid hormone, they ought to ask their doctor to check their thyroid. Especially when symptoms are obscure, it is easy to overlook them, and that's why we encourage patients and physicians, when there is the consideration of thyroid disease, to do a TSH level test. It is a simple test, it is not expensive and it can give you a very good idea as to whether further testing or treatment is really necessary.
I think you also have to be aware of the fact that a lot of these symptoms (like weight gain, chronic fatigue, lethargy, decreased alertness and so forth) are very common complaints, and there are lots of people that have these types of complaints for whom the thyroid gland is perfectly normal. In most of those situations, the cause of these problems is more a matter of the need for more exercise, the need for a better diet, less stress, or rest or better quality of rest.