The thyroid is a small gland that helps regulate a person's metabolism by producing hormones.
Problems can occur if the thyroid overproduces hormones, when it is known as hyperthyroidism, or underproduces hormones, which is called hypothyroidism. These issues may also result in the growth of the thyroid, which is called a goiter.
Researchers estimate that about 13 million people have an undiagnosed thyroid condition in the United States.
This article looks at the different types of thyroid disorders, what causes them, what their symptoms are, and how doctors diagnose and treat them.
Hypothyroidism is when a person's thyroid does not produce enough thyroid hormone. It is a more common thyroid issue than hyperthyroidism.
Not having enough thyroid hormone can slow down a person's metabolism. Hypothyroidism is especially common in women.
Causes of hypothyroidism include:
- Hashimoto's thyroiditis
- surgical removal of part or all of the thyroid gland
- radioactive iodine treatment for hyperthyroidism
- radiation therapy for head and neck cancers
- some medications, such as lithium for bipolar disorder and sulfonylureas for diabetes
- damaged or missing thyroid gland, often occurring from birth
- too much or too little iodine intake in the diet
- Turner syndrome, a chromosomal disorder affecting females
- pituitary gland damage
The most common cause of hypothyroidism is Hashimoto's thyroiditis, which is an autoimmune disorder. It is sometimes called Hashimoto's disease or shortened to Hashimoto's.
The exact cause of Hashimoto's is unclear, but heredity may play a role, and having a close family member with the condition may increase a person's risk.
Development of the disease can be very slow, occurring over months or even years.
Hypothyroid symptoms can vary, but may include:
A person may also develop a goiter, or enlargement of the thyroid gland. This condition happens because the gland tries to compensate for the lack of thyroid hormone.
After discussing a person's symptoms and family history, a doctor may recommend a blood test to check for hypothyroidism.
This test looks for a high level of thyroid-stimulating hormone (TSH) in a person's blood. The body releases TSH to signal the thyroid gland to release thyroid hormone.
When the body senses low levels of thyroid hormone, it releases more TSH, so a high level of TSH typically indicates hypothyroidism.
Alternatively, a doctor may test for a low level of the thyroid hormone, which is known as thyroxine.
There is no cure for hypothyroidism, but a person can manage it with thyroid hormone replacement.
A person typically takes thyroid hormone replacement orally, once a day as a pill, for the rest of their life.
Hyperthyroidism is when a person has too much thyroid hormone in their body, which speeds up their metabolic processes.
Hyperthyroidism is most often due to an autoimmune problem called Graves' disease that causes the whole thyroid gland to make too much thyroid hormone.
It is not clear why people develop Graves' disease, although researchers believe that genetics plays a role.
Graves' disease is an autoimmune condition because it occurs when a person's immune system creates antibodies that signal the thyroid gland to grow and produce significantly more thyroid hormone than the body needs.
Another cause of hyperthyroidism is called multinodular goiter. This condition is the result of one or more hormone-producing nodules in the thyroid gland that enlarge and release excess thyroid hormone.
Two problems that cause a high thyroid hormone level without having an overactive thyroid gland are:
- Thyroiditis, a temporary inflammation of the thyroid gland due to an autoimmune condition or a virus. The same illness can also cause hypothyroidism.
- Taking thyroid hormone replacement for an underactive thyroid.
According to the American Thyroid Association, common symptoms of hyperthyroidism can include:
- an initial increase in energy
- fatigue over timesweating
- rapid pulse
- tremors in the hands
- problems sleeping
- thin skin
- fine and brittle hair
- muscle weakness
- frequent bowel movements
- unintended weight loss
- a light menstrual flow or fewer periods
A person with Graves' disease may also experience inflammation of the eyes. This pushes the eyes forward, and they appear to bulge out.
However, only 5 percent of people with Graves' disease have their vision severely or permanently affected.
The overstimulation of the thyroid gland often makes it enlarge, which is called a goiter.
When diagnosing hyperthyroidism, a doctor will look for key symptoms, including an enlarged thyroid, a rapid pulse, tremors in the fingers, and moist, smooth skin.
As with hypothyroidism, they will also use laboratory tests that measure the amount of thyroid hormone and TSH in a person's blood.
When people have hyperthyroidism, the body senses the high level of thyroid hormone in the blood and stops releasing TSH. As a result, tests show a low level of TSH. Other tests can then be done to determine the cause of the condition.
A doctor may recommend beta-blockers as a short-term treatment for hyperthyroidism. Beta-blockers stop some of the effects of the thyroid hormone and quickly reduce some of the symptoms, such as a rapid pulse and tremors.
According to the American Thyroid Association, a doctor may also suggest a more permanent treatment:
- Antithyroid drugs: These stop the thyroid from making so much thyroid hormone.
- Radioactive iodine tablets: Thyroid cells absorb the iodine. This treatment destroys them, and the gland's hormone overproduction stops.
- Surgery: This is done by a surgeon who removes part or all of the thyroid.
If a person takes radioactive iodine or undergoes surgery, their thyroid may no longer be able to produce enough hormones, and they may develop hypothyroidism. They would then require thyroid hormone replacement treatment.
Thyroid nodules are lumps on a person's thyroid. They can appear alone or in groups and are very common.
According to the American Thyroid Association, about 50 percent if people over 60 years of age have a thyroid nodule. However, the vast majority of thyroid nodules are harmless.
It is not clear why people develop thyroid nodules. Thyroid nodules do not typically cause symptoms, although there is a chance they may cause hyperthyroidism by becoming overactive.
A doctor will be able to feel thyroid nodules on a person's neck, during an examination. If they discover nodules, they may check for hyperthyroidism or hypothyroidism.
There is a small risk of thyroid nodules being cancerous. To check for this, a doctor can do an ultrasound or a fine-needle biopsy.
If there are any signs of cancer or possible risk of cancer in the future, a doctor will recommend removing the nodules. Depending on the type of cells found in a biopsy, and the risk of the nodule being cancer, a doctor may remove part or all of the gland.
There are many different thyroid disorders, but doctors typically categorize them into two groups: those that make the thyroid overactive and those that make it underactive.
Although the symptoms can be nonspecific, diagnosing a thyroid disorder is usually straightforward.
If a person is concerned that they may have a thyroid disorder, they should speak to a doctor about testing.