Thyroid Disorders Overview
The thyroid is a small endocrine gland inside the neck, located in front of the breathing airway (trachea) and below the Adam’s apple. It produces two thyroid hormones, tri-iodothyronine (T3) and thyroxine (T4), which circulate in the bloodstream to all tissues of the body.
Thyroid hormones act to control metabolism (the body’s ability to break down food and store it as energy, and the ability to break down food into waste products with a release of energy in the process).
How well the thyroid works is controlled by another gland called the pituitary. The pituitary gland is located at the base of the brain and produces thyroid-stimulating hormone (TSH). TSH circulates via the bloodstream to the thyroid gland where it activates the thyroid to produce more thyroid hormones.
Thyroid hormones influence virtually every other organ system in the body. They tell the organs how fast or slow the should work, and tell the body systems when to use energy (e.g., consume oxygen and produce heat).
Endocrinologists (physicians and scientists who study and care for patients with endocrine gland and hormone problems) have defined and studied several major disorders of the thyroid gland. We will describe them briefly here. You can link to any of the conditions that you may want to learn more about:
Hyperthyroidism: An overactive thyroid gland. (More on HYPERTHYROIDISM)
Too much thyroid hormone speeds up the body’s metabolism. Women get this condition more often than men, and it occurs in about 1% of women. One of the most frequent forms of hyperthyroidism is known as Graves’ disease (named after Dr. Robert Graves). This condition can run in families although the exact nature of the genetic abnormality is unknown.
Because the thyroid is producing too much hormone with this condition, the body develops an increased metabolic state, with the functions of many body systems speeding up and producing too much body heat.
Hypothyroidism: An underactive thyroid gland. (More on HYPOTHYROIDISM)
Several causes for this condition exist, most of which affect the thyroid gland directly, impairing its ability to make enough hormone. More rarely, there are conditions in the brain (for example, pituitary tumors) that cause the pituitary gland to fail to produce thyroid-stimulating hormone (TSH) and stimulate the thyroid enough to make hormone
Whether the problem is with the thyroid gland or the pituitary gland, the result is that the thyroid is not producing enough hormone, and most major body functions, both physical and mental processes, slow down. The body consumes less oxygen and produces less body heat.
Thyroid Nodules: A condition that begins as a small localized swelling or lump in the thyroid gland.
Thyroid nodules may be single or multiple. They represent enlargement of a collection of thyroid cells caused by thyroid cell growth or because of a local fluid collection (“cyst”) in the thyroid gland. Thyroid nodules are quite common. Significant sized nodules, which are greater than a half inch across, occurs in about 5% of people. Almost half of the population will have tiny nodules but many are not aware of them until they become large. (More on THYROID NODULES)
Although most of these nodules are benign, they need medical attention because:
- They may be cancer growths
- They may produce too much thyroid hormone (hyperthyroidism)
- They may become too large and press on your trachea (airway tube) or swallowing tube (esophagus)
Other thyroid problems include thyroiditis (inflammation of the thyroid gland), a goiter (enlargement of the thyroid gland, which can be visible); and thyroid cancer.
Hyperthyroidism more commonly affects women who are between ages 20 and 40, but men can also develop this condition. The symptoms can be frightening, especially if the person affected has no idea what is happening to them
Symptoms can include:
- Muscle weakness so that it can be difficult to walk up stairs or lift heavy things
- Trembling hands
- Rapid heartbeat
- Weight loss even though you are eating normally or excessively
- Diarrhea or frequent bowel movements
- Irritability and anxiety
- Eye problems (irritated eyes or difficulty seeing)
- Menstrual irregularities
- Intolerance to heat and increased sweating
Graves’ disease is the most common cause of hyperthyroidism. It occurs when the immune system produces antibodies that attack the thyroid gland. This causes the thyroid to enlarge and make too much thyroid hormone. This conditions happens often in people with a family history of thyroid disease. In some patients with Graves’ disease, one of the noticeable symptoms may be swelling behind the eyes that causes them to push forward or bulge.
Other causes of hyperthyroidism:
- Thyroid nodules (More on THYROID NODULES);
- Taking too much thyroid hormone medication to treat other conditions;
- Subacute thyroiditis (An inflamed thyroid gland, caused by a virus, that typically causes neck discomfort or tenderness near the thyroid gland. When the infection leaves, the condition improves.); or
- Lymphocytic thyroiditis and postpartum thyroiditis (These can cause the thyroid to become inflamed and release too much thyroid hormone into your system.).
Antithyroid Drugs: These drugs work to decrease the amount of hormone the thyroid gland makes. For some physicians, the preferred drug is methimazole (Tapazole) because it may need to be taken only once a day. For pregnant or lactating women, a drug called PTU (propylthiouracil) may be preferred.
Antithyroid drugs may have to taken for one to two years and sometimes longer. The condition may go away, but there could be a relapse, even years later. Therapy with antithyroid drugs is usually thought of as either short term or long term. Short term therapy is used to make the thyroid blood tests normal before a decision is made about definitive therapy. Long term therapy is used in some patients to try to make the disease remit even after the antithyroid drug is stopped.
Beta-blockers: Beta-blocker drugs, like atenolol, do not block the production of thyroid hormone. Instead they control many troubling symptoms, especially rapid heart rate, trembling, anxiety, and the high amount of heat the body produces with this condition
Radioactive iodine: The natural element, iodine, is normally collected by the thyroid gland out of the bloodstream. Radioactive iodine treatment involves taking a radioactive form of iodine that causes the permanent destruction of the thyroid. The response to treatment can take from 6 to 18 weeks. Because the radioiodine often destroys some of the normal function of the thyroid gland, people who have this therapy will very likely need to take thyroid hormone for the rest of their lives to control their hormone levels
Surgery: Removal of the thyroid gland (thyroidectomy) is another permanent solution, but is often the least preferred option. This procedure must be performed by a highly skilled and experienced thyroid surgeon because of the risk of damage to nerves around the larynx (voice box) and to the parathyroid glands, which control calcium metabolism in the body. Surgery is recommended when there is a large goiter that makes breathing difficult or when antithyroid drugs are not working, or when there are reasons not to take radioactive iodine. It may also be used in patients who have coexisting thyroid nodule(s), especially when a fine needle aspiration is suspicious for cancer. This circumstance is unusual.
After both radioactive iodine and surgery treatments, the patient will need to be monitored regularly for adequate thyroid hormone levels in the blood. After such treatment, most patients become hypothyroid (don’t produce enough thyroid hormone) and need to take a supplement of thyroid hormone once a day.
Hypothyroidism, if not treated, can become a very dangerous condition. The condition occurs when the thyroid gland does not produce enough thyroid hormone – the opposite of hyperthyroidism.
Instead of the body systems speeding up and overheating, they slow down in a variety of ways. With hypothyroidism, a person may:
- Become sluggish and tire easily
- Gain weight more easily
- Become cold more easily or have trouble withstanding cold weather
- Have less perspiration
- Have drier skin
- Have coarser or thinner hair
- Get mild swelling around your eyes (if you have hypothyroidism because of treatment for Graves’ disease you may still have eyes that seem to bulge and stare)
- Have a high blood cholesterol
- Have a weaker heart and slower heart rate
- Have decreased lung function and shortness of breath
- Have slower digestion and constipation.
- Have menstrual irregularities or infertility
NOTE: Rarely, a life-threatening condition called myxedema can develop with severe hypothyroidism. If you have trauma to your body (injury), an infection, exposure to cold, or take certain drugs, these things can bring on myxedema coma. You may develop a very low body temperature and lose consciousness. Myxedema coma is very unusual in patients who are known to be hypothyroid and are prescribed levothyroxine replacement. Indeed, if it occurs in this circumstance it most likely is related to poor compliance. On the other hand, myxedema coma is slightly more common in patients who have never been diagnosed as having hypothyroidism as the initial symptoms are nonspecific and the progression of the disease is insidious.
Infants with hypothyroidism are usually identified through testing after birth. This is important, because if hypothyroidism is not corrected, a child could have mental slowness or retardation problems and not grow to a normal height.
Hypothyroidism can be traced to:
- A problem in the thyroid gland
- Drugs or diseases that affect thyroid function
- The pituitary gland that does not make enough thyroid-stimulating hormone (TSH)
- Treatment for hyperthyroidism (too much thyroid hormone) with radioactive iodine or surgery
Hypothyroidism is treated by replacing the thyroid hormone the body needs. This is usually done with an oral tablet or pill of the thyroid hormone levothyroxine, thyroxine or T4. Although not recommended except in unusual cases, a patient may be given T3, or a combination of T3 and T4. A person will usually notice an improvement in their health within two weeks. However, bad cases of hypothyroidism may take longer to correct.
Most patients with hypothyroidism will need to be on T4 treatment for the rest of their life. They have to work closely with their doctor, take their medication as directed, and be monitored regularly in case the dose of the medication needs to be adjusted. If too much T4 is taken, a person can develop a mild case of hyperthyroidism. If they don’t get enough, the symptoms of hypothyroidism will return.
A patient may need special attention if they are:
- Older or have a weak heart – Thyroid hormone can make the heart work harder. A lower dose may be needed.
- Pregnant – Higher doses may be needed and another adjustment after delivering the baby. Also, while pregnant frequent monitoring is required and the thyroid hormone dosage may change.
- Having surgery – A person should have enough T4 in their system before surgery so that they can tolerate the anesthesia and have a satisfactory recovery. If the patient is not able to take medicine by mouth, T4 can be given intravenously after surgery.
About 90 to 95% of all thyroid nodules are not harmful or cancerous. A person may not be aware that they have a nodule, but if it starts to grow, they may notice it. A doctor may feel it when he or she carefully examines the thyroid gland.
Nodules should be checked by a doctor. Tests, especially a fine needle aspiration, can usually tell if a nodule is harmless and which treatment would be best. A nodule may be cancerous if the lymph nodes under the jaw are swollen and if it:
- Grows quickly and feels solid
- Causes pain
- Feels hard
- Causes difficulty with swallowing or breathing
- Causes a person to be hoarse
If a patient has had radiation treatment around the head or neck areas, they should tell their doctor because this can increase your chances of having nodules and cancer.
Among people who have thyroid nodules, thyroid cancer is found in about 8% of men and 4% of women. To determine whether a nodule may be harmful, the doctor may:
- Perform a fine-needle aspiration biopsy, in which a thin needle is inserted into the nodule to remove cells and/or fluid samples from the nodule for examination under a microscope;
- Perform a thyroid scan with a radioactive marker to learn whether the nodule is functioning normally;
- Take blood and perform several tests, including measuring levels of thyroid-stimulating hormone (TSH), antibody tests, and calcitonin tests; or
Perform a thyroid hormone treatment and see if the nodule shrinks, which probably means it is not malignant. (The use of thyroid hormone for the purpose of shrinking nodules, and therefore helping to assess their chance of harboring malignancy, is being used less frequently now than in the past. This change in approach is related to the increased utility of the fine needle aspiration, recognition that even thyroid nodules with thyroid cancer may get somewhat smaller, and because there may be adverse side effects on the heart and bones from the thyroid hormone medication. The dose of thyroid hormone used to shrink thyroid nodules is higher than that used for simple replacement purposes. Thyroid hormone replacement should not be associated with these adverse effects.)
Only about 5% of thyroid nodules are cancerous. If you have thyroid cancer, please remember that most patients recover well from this type of cancer. Most thyroid cancers need to be removed by surgery, after which radioactive iodine therapy may be needed to destroy any remaining thyroid cells.
Other types of nodules, even if they are not cancerous, may also need to be removed. Most specialists recommend a total rather than partial removal of the thyroid gland. The thyroid gland and the nodules within it are removed by surgery (thyroidectomy) with T4 treatment afterward.
Following surgery and subsequent radioactive iodine therapy, patients with thyroid cancer do still require monitoring for many years. The monitoring varies between patients but typically includes periodic blood tests, including tests for thyroid function and thyroglobulin levels (a tumor marker), as well as possibly radiologic studies to include sonograms, CT scans, MRI scans and radioactive scans. The use of these tests varies based on the type of tumor, and may also vary between institutions.
Overfunctioning (“autonomous”) nodules are almost always not malignant, but they may act like thyroid tissue, produce extra hormones, and cause hyperthyroidism (too much hormone production). These nodules may be surgically removed or treated with radioactive iodine.
If a nodule has fluid it is called a cyst. To treat it, the doctor will probably drain it or monitor it for change. If these nodules bleed a lot or come back, then they may need to be removed.
Thyroid Disorders Lifestyle and Prevention
Patient who have been treated for a thyroid conditions should understand:
- When to take their thyroid hormone medication
- Signs or symptoms of too much or not enough thyroid hormone
- When to go to their doctor for blood tests to check thyroid hormone levels, or to check for nodules
- That other drugs (and even other medical conditions) you are taking could affect your health or interact with your thyroid medication. Ask your doctor about possible interactions, side effects, or warning signs.
In general, there are things you can do to protect your health. Eating a balanced diet, getting enough sleep, exercising several times a week, and getting fresh air and relaxation are all activities that will help you feel your best. Healthy living is an important part of recovery from a thyroid condition. These suggestions may also help to prevent future problems.