Facts on Thyroid Problems
The thyroid gland is located on the front part of the neck below the thyroid cartilage (Adam's apple). The gland produces thyroid hormones, which regulate metabolic rate (how fast calories are consumed to produce energy). Thyroid hormones are important in regulating body energy, body temperature, the body's use of other hormones and vitamins, and the growth and maturation of body tissues.
Diseases of the thyroid gland can result in either production of too much (overactive thyroid disease or hyperthyroidism), too little (underactive thyroid disease or hypothyroidism) thyroid hormone, thyroid nodules, and/or goiter. Thyroid problems are much more common in women than in men.
- Production of thyroid hormones: The process of hormone synthesis begins in a part of the brain called the hypothalamus. The hypothalamus releases thyrotropin-releasing hormone (TRH). The TRH travels through the venous plexus located in the pituitary stalk to the pituitary gland, also in the brain. In response, the pituitary gland then releases thyroid-stimulating hormone (TSH, also called thyrotropin) into the blood. The TSH travels to the thyroid gland and stimulates the thyroid to produce the two thyroid hormones, L-thyroxine (T4) and triiodothyronine (T3). The thyroid gland also needs adequate amounts of dietary iodine to be able to produce T4 and T3, the molecules of which contain four and three atoms of iodine, respectively.
- Regulation of thyroid hormone production: To prevent the overproduction or underproduction of thyroid hormones, the pituitary gland senses how much hormone is in the blood and adjust the production of hormones accordingly. For example, when there is too much thyroid hormone in the blood, TRH and TSH production are both decreased. The sum effect of this is to decrease the amount of TSH released from the pituitary gland and to reduce production of thyroid hormones from the thyroid gland to restore the amount of thyroid hormone in the blood to normal. Defects in these regulatory pathways rarely may result in hypothyroidism (underactive thyroid problem) or hyperthyroidism (overactive thyroid problem). The most common cause of hypothyroidism and hyperthyroidism occurs due to problems within the thyroid and not the regulatory system.
- Thyroid goiter: Thyroid goiter is any enlargement of the thyroid that can occur with hyperthyroidism or hypothyroidism but also with benign and malignant (cancerous) nodules. Worldwide, the most common cause of goiter is iodine deficiency. Although it used to be very common in the U.S., it is now less common with the use of iodized salt. Multiple nodules in the thyroid are very common, but only about 5% of the nodules are a thyroid cancer. Thyroid cancer rates have been increasing steadily by about 6% every year for more than 20 years. It is one of the few cancers whose rate is increasing and whose very low rate of mortality is also rising with time. Although radiation exposure as a child can increase the risk of thyroid cancer, we do not know why the overall rate has been increasing. Thyroid cancer is diagnosed after a thyroid ultrasound exam and a needle aspiration biopsy of the nodule.
What Causes Hypothyroidism in Pregnancy?
Newly diagnosed hypothyroidism in pregnancy is rare because most women with untreated hypothyroidism do not ovulate or produce mature eggs in a regular manner, which makes it difficult for them to conceive.
It is a difficult new diagnosis to make based on clinical observation. The signs and symptoms of hypothyroidism (fatigue, poor attention span, weight gain, numbness, and tingling of the hands or feet) are also prominent symptoms of a normal pregnancy.
Undiagnosed hypothyroidism during pregnancy increases the chance of stillbirth or growth retardation of the fetus. It also increases the chance that the mother may experience complications of pregnancy such as anemia, eclampsia, and placental abruption.
Probably the largest group of women who will have hypothyroidism during pregnancy are those who are currently on thyroid hormone replacement. The ideal thyroxine replacement dose (for example, levothyroxine [Synthroid, Levoxyl, Levothroid, Unithroid]) may rise by 25% to 50% during pregnancy. It is important to have regular checks of T4 and TSH blood levels as soon as pregnancy is confirmed; and frequently through the first 20 weeks of pregnancy to make sure the woman is taking the correct medication dose. It is recommended that the levothyroxine dose be adjusted to keep the TSH level < 2.5 mIU/L during the first trimester of pregnancy and < 3 mIU/L during the last two trimesters of pregnancy. Usually the increase in thyroid hormone needed during pregnancy disappears after the delivery of the baby and the pre-pregnancy dose of levothyroxine can be resumed immediately post-partum.
What Causes Hyperthyroidism in Pregnancy?
Newly diagnosed hyperthyroidism occurs in about 1 in 2,000 pregnancies. Graves' disease accounts for 95% of cases of hyperthyroidism newly diagnosed during pregnancy.
As with hypothyroidism, many symptoms of mild hyperthyroidism mimic those of normal pregnancy. However, anyone experiencing symptoms such as significant weight loss, vomiting, increased blood pressure, or persistently fast heart rate should have blood tests to evaluate whether hyperthyroidism is present.
Mild or subclinical hyperthyroidism defined as a lower than normal TSH and normal Free T4 level is not dangerous to the mother or baby and does not need to treated. Thyroid tests should be checked again in 4 weeks. However, untreated moderate to severe hyperthyroidism does cause fetal and maternal complications including poor weight gain and tachycardia (an abnormally fast heart rate).
There are new recommendations for the treatment of hyperthyroidism during pregnancy Propylthiouracil is used during the first trimester to block the synthesis of thyroid hormone and to bring thyroid hormone levels to borderline or slightly higher than normal levels. Propylthiouracil has a lower risk of some rare fetal malformations compared to methimazole (Tapazole) and is preferred during the critical fetal developmental period during the first trimester. Propylthiouracil is not recommended during the remainder or pregnancy because of the risk of serious hepatitis. During the second and third trimester, propylthiouracil should be switched to methimazole. The incidence rate of side effects for each medication is not increased in pregnancy.
Iodine will cross the placenta, so its use in either a thyroid scan or in treatment with radioactive iodine is prohibited in pregnancy.
One positive note for women with hyperthyroidism is that those with Graves' disease or Hashimoto's thyroiditis may have improvement in their symptoms as the pregnancy progesses.
Does Pregnancy Make Goiters Larger?
It is common for a goiter to enlarge slightly during pregnancy. It is more common when the mother lives in an area of iodine deficiency. In the United States, the average intake of iodine is adequate but can be low if someone avoids consumption of milk, eggs, and iodized salt. Not all prenatal vitamins contain iodine, but it is recommended that only prenatal vitamins that contain iodine should be used during pregnancy. If a thyroid nodule is found during pregnancy, new recommendations are not to wait until the end of pregnancy, but to arrange for an evaluation and possible biopsy as soon as possible.
What Is Postpartum Thyroid Disease?
Some women may have temporary thyroiditis called postpartum subacute thyroiditis that usually occurs within 3 to 6 months after giving birth. It also may occur after miscarriage. The classic clinical picture is a woman who will first have symptoms of hyperthyroidism with palpitations, anxiety, and weight loss, followed by hypothyroidism with fatigue, constipation, and weight gain, culminating in normal thyroid function in 90% of women of experience this condition.
Women with type I diabetes have a 25% risk of developing postpartum thyroid dysfunction.
Consult your doctor if you have symptoms of hypothyroidism or hyperthyroidism after pregnancy or miscarriage.
What Causes Thyroid Problems?
- Loss of thyroid tissue: Treatment of hyperthyroidism by radioactive destruction of thyroid tissue or surgical removal of thyroid tissue can result in hypothyroidism.
- Antithyroid antibodies: These may be present in people who have type 1 diabetes, lupus, rheumatoid arthritis, chronic hepatitis, or Sjogren's syndrome. These antibodies may cause decreased production of thyroid hormones because of thyroid destruction. Hashimoto's thyroiditis, the most common cause of hypothyroidism in an adult, occurs because of autoimmune destruction of the thyroid results in a decreased production of thyroid hormone and an increased amount of TSH.
- Congenital defects in the production of thyroid hormone: Hypothyroidism can be present from birth. This is commonly discovered early with nationwide newborn screening for this disease. When one of the steps in thyroid hormone synthesis is defective, the production of thyroid hormone is reduced, with a subsequent increase in TSH. The increased TSH results in a goiter (enlargement of the thyroid gland itself that can be seen as an obvious swelling in the front of the neck). If the metabolic block is severe, thyroid hormone levels are low begining at birth, resulting in mental retardation, goiter, and short stature (hypothyroid cretinsim).
- Medications: Some medications, particularly lithium (Eskalith, Lithobid), may cause a drug-induced hypothyroidism.
- Graves' disease: This autoimmune thyroid condition results from abnormal stimulation of the thyroid gland by a material in the blood termed the thyroid stimulating immunoglobulin (TSI). TSI overstimulates the thyroid causing a goiter. It also causes Grave's eye disease, including a "bug-eyed" look and "frightened stare." This can progress to severe eye pain or eye muscle weakness causing tearing and double vision. In severe cases, the swelling of the eye and surrounding tissue can cause loss of vision. It also causes raised, thickened skin over the shins or tops of the feet.
- Toxic multinodular goiter: This occurs when a nodule in the thyroid gland produces thyroid hormones all by itself, without regard to the degree of TSH stimulation. It usually occurs in people with a long-standing goiter, usually in the elderly. Toxic multinodular goiter is different from Graves' disease because of the general lack of eye complications and less severe signs of hyperthyroidism.
- Subacute thyroiditis: This temporary inflammatory disorder of the thyroid gland includes such conditions as de Quervain's thyroiditis or postpartum subacute thyroiditis. In these conditions, there may be periods of increased thyroid hormone release due to the inflammation, causing excess thyroid hormone to be released. After the all the thyroid hormone has leaked out of the damaged tissue, a temporary hypothyroid period begins and can last 2-4 months. Usually 90% of people with this condition will go back to normal thyroid function without treatment.
- Pituitary adenoma: This tumor of the pituitary gland causes independent TSH production leading to overstimulation of the thyroid gland.
- Drug-induced hyperthyroidism: This is most commonly caused the the heart medication amiodarone (Cordarone).
Goiter or Nodules Causes
- Most of the time thyroid nodules and thyroid goiters do not cause any symptoms. Some goiters are found because of the thyroid hormone overproduction or underproduction from the thyroid gland. Some nodules are found because a patient or doctor sees or feels a lump in the neck. If the goiter becomes very large, the person may feel a pressure in the front of the neck with swallowing hard or firm foods such as bread crusts or meat. This pressure may also cause a small dry chronic cough. It is rare that the thyroid can become large enough to completely block swallowing or breathing.
- Nodular or multinodular goiter: This is a condition in which multiple nodules form in the thyroid. There are only two conditions that cause thyroid enlargement and nodules: 1) external radiation exposure, or 2) iodine deficiency. Often several members of a family. will have an enlarged goiter as the condition can be inherited
- Thyroid cancer: There are several types of thyroid cancer. The most common type, papillary thyroid carcinoma, occurs in more than 85% of cases. This type of cancer can be caused by radiation exposure as a child or adolescent, including therapeutic radiation used in the treatment of cancers or in accidents such as the Chernobyl nuclear disaster. Most of the time, the reason for developing thyroid cancer is unknown.
What Are the Signs and Symptoms of Hypothyroidism (Low Thyroid Hormone Level)?
Symptoms of hypothyroidism in infants can include:
- Poor feeding
- Poor growth
- Jaundice (yellow discoloration of the skin and eyes)
- Excessive sleeping
Symptoms of hypothyroidism in children include:
- Symptoms similar to adult symptoms
- Excessive fatigue
- Poor growth
- Delayed tooth development
- Delayed sexual maturation
- Poor school performance
Symptoms of hypothyroidism in adults include:
- Poor appetite
- Weight gain
- Dry skin
- Hair loss
- Intellectual ability worsens
- Deeper, hoarse voice
- Puffiness around the eyes
- Irregular menstrual periods or lack of menstrual periods
What Are Signs and Symptoms of Hyperthyroidism (Overactive Thyroid)?
Symptoms of hyperthyroidism in children include:
- Symptoms similar to adult symptoms
- Declining school performance
- Behavior problems
- Hyperkinesis (the need to move all of the time)
Symptoms of hyperthyroidism in adults include:
- Hand tremors
- Feeling excessively hot in normal or cold temperatures
- Frequent bowel movements
- Losing weight despite normal or increased appetite
- Excessive sweating
- Menstrual period becomes scant, or ceases altogether
- Joint pains
- Difficulty concentrating
- Eyes seem to be enlarging
Symptoms of hyperthyroidism in the elderly may cause:
What Are the Signs and Symptoms of Thyroid Nodules and Goiter?
- The only sign of goiter or nodule is an enlargement in the lower part of the front part of the neck. This enlargement is often not painful or bothersome.
- When the nodule or goiter becomes large, there can be pressure on the surrounding normal structures in the neck including the esophagus (swallowing tube), trachea (breathing tube) and the blood vessels that bring blood to and from the head. A common symptom is feeling a constant pressure in the front of the neck that is worse when the head is tilted down. This pressure on the breathing tube (trachea) may cause a small, dry cough that can be constant and worsens when lying down. The pressure on the swallowing tube (esophagus) may be noticed as difficulty in swallowing large pills or dry food such as bread and rice with the food "getting stuck" in the lower part of the front of the neck. Rarely, this pressure can damage the nerve that controls the voice box, causing hoarseness of the voice.
When Should You See a Doctor for Thyroid Problems?
The signs and symptoms of hypothyroidism and hyperthyroidism typically develop slowly over a period of weeks to months. If an individual has prolonged symptoms or signs of either condition, call a doctor to be evaluated.
Untreated hypothyroidism may have severe effects on the brain as well as cause intestinal obstruction and inability of the heart to beat effectively. An infection, exposure to cold, trauma, and certain medications may often cause a worsening of hypothyroidism.
Seek immediate attention at a hospital's emergency department if you have these signs and symptoms associated with thyroid problems.
Severe hyperthyroidism, called thyrotoxic crisis (thyroid storm), may be life-threatening because of its effects on the heart and brain. It often occurs in people who are untreated or are receiving inadequate treatment for thyroid problems. A severe infection can also cause a thyrotoxic crisis.
Seek immediate attention at a hospital's emergency department if you have these signs and symptoms associated with thyroid problems.
- Chest pain
- Rapid and/or irregular heartbeat
- Shortness of breath
- Abdominal pain
- Extreme agitation or irritability
- Disorientation (person has no knowledge of the date or location)
Severe goiter or nodule problem: Seek immediate attention at a hospital's emergency department if you have these signs and symptoms associated with thyroid problems.
- Shortness of breath especially with stridor (a whistling sound in your neck when you breathe)
- Extreme pain in your thyroid gland that prevents you from swallowing
- Sudden enlargement of your thyroid gland, especially if associated with problems breathing or swallowing
- Pain and high fever with the thyroid enlargement
How Are Thyroid Problems Diagnosed?
The medical history and physical exam are important parts of the evaluation for thyroid problems. The health care practitioner will focus on eye, skin, cardiac (heart), and neurologic findings.
- Thyroid-stimulating hormone (TSH): In most cases, this is the single most useful lab test in diagnosing thyroid disease. When there is an excess of thyroid hormone in the blood, as in hyperthyroidism, the TSH is low. When there is too little thyroid hormone, as in hypothyroidism, the TSH is high.
- Free (T4): T4 is one of the thyroid hormones. High T4 may indicate hyperthyroidism. Low T4 may indicate hypothyroidism.
- Triiodothyronine (T3): T3 is another one of the thyroid hormones. High T3 may indicate hyperthyroidism. Low T3 may indicate hypothyroidism.
- TSH receptor antibody (TSI): This antibody is present in Graves' disease.
- Antithyroid antibody (thyroperoxidase antibody): This antibody is present in Hashimoto's and Graves' disease.
Nuclear thyroid scan: During this scan a small amount of radioactive iodine is swallowed or a similar material, 99m-technetium, is injected into the blood, and then an imaging study of the thyroid is taken that reveals localization of the radioactivity. Increased uptake of the radioactive material in the thyroid gland indicates hyperthyroidism, while decreased uptake is present in hypothyroidism. This test should not be performed on women who are pregnant.
Thyroid ultrasound: Thyroid ultrasound helps to determine the size and number as well as the different types of nodules in the thyroid gland. This exam can also detect if there are enlarged parathyroid glands or lymph nodes near the thyroid gland.
Fine-needle aspiration: During this procedure, a thin needle is inserted into the thyroid gland in order to get a sample of thyroid tissue, usually from a nodule. This test can be done in a health care practitioner's office without special preparations. It is recommended that the biopsy be performed with ultrasound guidance. The tissue is then observed under a microscope by a pathologist to look for any signs of cancer.
Computerized axial tomography (CT) scan: A CT scan is occasionally used to look for the extent of a large goiter into the upper chest or to look for narrowing or displacement of the trachea (breathing tube) from the goiter. However, this is not a routine test for thyroid nodules or goiter.
What Are the Treatments and Medications for Thyroid Problems?
Medications for Hyperthyroidism
- Beta-blockers: This class of medication works by blocking many of the body's responses to hyperthyroidism. It decreases tremor, nervousness, and agitation. It also reduces the fast heart rate. Beta blocker tablets are prescribed to a patient with mild to moderate symptoms of hyperthyroidism, and as an IV preparation to the person with the severe form of hyperthyroidism (thyrotoxic crisis). Although beta blockers block the responses to hyperthyroidism, it does not treat the underlying cause.
- Propylthiouracil: This antithyroid drug works by blocking thyroid hormone synthesis. It takes several months after starting the medication for the full therapeutic effect to be achieved. The US FDA has issued a guidance that this drug should be used only during the first trimester of pregnancy, or if there is an intolerance to thimazole. Common mild side effects include an itchy rash. More rare, serious side effects include a decrease in white blood cell count, which can decrease the ability to fight off infection. Therefore, a high fever should prompt a call to the doctor.
- Methimazole (Tapazole): This is the preferred antithyroid drug in everyone except women in the first trimester of pregnancy for hyperthyroidism. This antithyroid drug also works by blocking thyroid hormone synthesis. It may take slightly longer than propylthiouracil to achieve its full effect. It has similar side effects as propylthiouracil.
- Iodide (Lugol's solution, Strong iodine): This medication works by inhibiting the release of thyroid hormone from the overfunctioning thyroid gland. It must be used in conjunction with an antithyroid drug because the iodine can be used to increase the amount of thyroid hormone produced and worsen the hyperthyroidism. Common side effects include nausea and a metallic taste in the mouth.
- Radioactive iodine therapy: An endocrinologist or nuclear medicine specialist can treat overactive thyroid conditions with radioactive iodine swallow. This is generally a different type of radioactive iodine than used for diagnostic scans. This treatment takes several months to work by scarring down the thyroid gland, resulting in a smaller- sized gland, often accompanied by hypothyroidism.
Medications for Hypothyroidism
- L-thyroxine (Synthroid, Levoxyl, Levothroid, Unithroid, Tirsosint): This medication is the mainstay of thyroid hormone replacement therapy in hypothyroidism. This is a synthetic form of thyroxine. This is exactly the same hormone that the thyroid makes. The body tissues convert it to the active product L-triiodothyronine. Side effects are rare, and it has an excellent safety record. Tirsosint is a new liquid form of levothyroxine in a gelcap that may be easier to absorb in the bloodstream.
- Triiodothyronine: This is rarely used alone as thyroid hormone replacement, because it has a much shorter persistence in the blood than L-thyroxine. Its use can cause rapid increases in triiodothyronine concentration, which can be dangerous in the elderly and in people with cardiac disease. It may be used in combination with L-thyroxine for people who have poor symptomatic relief with L-thyroxine alone.
- Thyroid extract or "natural" thyroid hormone: This is dried and powdered pig thyroid gland. The hormone is not purified and the exact amount of T4 and T3 can be variable. This is not recommended as a thyroid hormone replacement. There is an excess of T3 in this preparation.
Medications for Thyroid Nodules and Goiter
- If the thyroid function is abnormally high or low, then the treatments are as described above.
- If the thyroid function is normal with thyroid nodules, there are no good medical treatments to shrink the nodules and surgery is usually suggested. Many years ago it was standard of care to give levothyroxine to "shrink" nodules, but it was found after careful research that administration of thyroid hormone rarely shrinks large nodules.
- An emerging treatment of nontoxic goiters/nodules is radioactive iodine therapy. This therapy is used commonly in Europe and South America but is not yet commonly used in all patients in the United States. This treatment is considered when a patient has a large goiter and there are medical problems that prevent a surgical treatment.
What Are The Supplements and Remedies for Thyroid Disease?
It can be very dangerous to take supplements for your thyroid condition without consulting a doctor. Supplements that contain large amounts of iodine such as seaweed can make thyroid hormone levels go very high if you have nodular goiter, or very low if you have a history of an autoimmune thyroid condition such as Hashimoto's thyroiditis or Graves' disease. There is no scientific evidence that herbal supplements, yoga poses, natural thyroid treatments, or natural thyroid remedies improve thyroid health and function. Dietary supplements are not regulated by any agency and therefore there is no quality control of these supplements. It is not recommended that any supplement be taken for thyroid health.
Is There Surgery for Thyroid Problems?
Surgery for hyperthyroidism (thyroidectomy), large thyroid nodules, or nontoxic goiters may involve removal of much of the thyroid tissue, leaving some intact to continue to produce thyroid hormone. Risks of this procedure include damage to the nerves that control the vocal cords, damage to the parathyroid glands (resulting in low calcium levels), which lie just behind the thyroid gland, and bleeding. Hypothyroidism may also occur, but occurs less frequently than with radioactive iodine treatment. Persistent hyperthyroidism may also occur. If so, the entire thyroid gland is removed. In general, in the hands of an experienced surgeon, this is considered an effective and relatively safe procedure.
About 70% of patients who retain half of their thyroid gland will continue with normal thyroid function after the surgery. Those patients who have the entire thyroid removed must take thyroid hormone for the rest of their lives. Patients with thyroid cancer will need special treatments and scans with radioactive iodine. Most patients with thyroid cancer are managed by endocrinologists and not oncologists.
What Is the Follow-up for Thyroid Disease?
Anyone diagnosed with Graves' disease should stop smoking immediately because smoking increases the risk of progression to Graves' eye disease.
Follow the medication schedule prescribed by your health care professional. Ask your doctor or pharmacists what side effects the medications may cause. Also discuss with your doctor the kinds of symptoms that would prompt a call to the doctor or a visit to the emergency department.
How Do You Prevent Thyroid Problems?
There is no known way to prevent hyperthyroidism or hypothyroidism. In the United States, iodine deficiency is rare, so there is no way to prevent goiter or thyroid nodules. It is not recommended that a person take extra iodine. Instead, there is plenty of iodine in an adult multiple vitamin supplement if it contains iodine. Read the ingredient label to make sure the vitamin contains iodine.
Radiation will induce both benign and malignant thyroid nodules. Individuals should avoid excess radiation or unnecessary CT scans of the head and neck and use a "thyroid shield" when dental X-rays are performed.
What Is the Prognosis for Thyroid Problems?
Most people with either hypothyroidism, hyperthyroidism, and benign and malignant thyroid nodules, with proper diagnosis and treatment, can control their condition with no long-term effects and a normal life expectancy. However, those with undiagnosed disease may progress to hypothyroid coma or thyrotoxic crisis (thyroid storm), with death rates approaching 50%.
Graves' eye disease has been treated with corticosteroid medication, radiotherapy, and surgery with varying success.
Patients with thyroid cancer have a very low mortality rate (<5%) but the overall risk depends on age, type of thyroid cancer, and the extent of spread of the tumor. Endocrinologists will manage the evaluation and treatment of thyroid cancer, rather than an oncologist.