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HEALTH GUIDE / Prescription Drugs / Thyroid Medications

Thyroid Medications

Thyroid Medication, Thyroid hormone


About thyroid medications

Thyroid medications are drugs used to control symptoms related to various forms of thyroid disease. Some of these drugs help to shrink the thyroid. Other medications provide hormones to the body when the thyroid is too damaged to produce the substance naturally.

Several types of thyroid medications are available. They include antithyroid medications, thyroid hormone, beta blockers and radioactive iodine therapy.

Antithyroid medications are used to treat hyperthyroidism by preventing the thyroid gland from producing excess levels of hormones. Patients typically begin to feel better within two to 12 weeks of beginning treatment. Treatment regimens often last up to a year or longer. Though these drugs are effective, some patients may experience a relapse of their condition later. Examples of these drugs include methimazole (Tapazole) and propylthiouracil (PTU).

Thyroid hormone is usually a synthetic version of natural thyroid hormones thyroxine (T4) and/or triiodothyronine (T3). They can be used for two different treatment purposes. In most cases, thyroid hormone is given to patients whose thyroid does not function efficiently enough to provide their body with the amount of hormone it requires, a condition called hypothyroidism. However, the drug also can be used to suppress further growth of thyroid tissue, although there is some controversy about the effectiveness of this therapy.

The U.S. Food and Drug Administration (FDA) warns against using thyroid hormone in an attempt to treat obesity in people with normal thyroid function. High doses may cause serious or even life-threatening toxicity, especially if combined with amphetamine diet pills. The agency has also warned in the past against purported weight-loss supplements that actually contain strong thyroid hormones which could cause heart attack, stroke or other serious conditions.

In addition, thyroid hormone should not be used in an attempt to treat female or male infertility that is not accompanied by hypothyroidism, the FDA advises.

Brands of synthetic thyroid hormone may include additional ingredients that differ from other versions. These medications include:

  • levothyroxine (L-Thyroxin, Levolet, Levo-T, Levothroid, Levoxyl, Novothyrox, Synthroid, Thyro-Tabs, Unithroid)
  • liothyronine (Cytomel)
  • liotrix (Euthroid, Thyrolar)

Concerned that thyroxine generics might not be equivalent to branded drugs, the American Association of Clinical Endocrinologists, the American Thyroid Association and The Endocrine Society recommend staying with one preparation and avoiding substitutions.

There are also natural hormonal preparations made from animal thyroid. Desiccated thyroid is derived from cattle or pigs. Thyroglobulin, derived from pigs, is no longer available in the United States.

Beta blockers are antihypertensives primarily prescribed for cardiovascular conditions including high blood pressure, angina, heart attack and heart failure. However, they are also effective in treating symptoms associated with hyperthyroidism, including rapid heart rate, trembling, anxiety and excessive body heat. Patients should inform the physician if they have low blood pressure, prediabetes or diabetes, or if they are already taking an antihypertensive. Examples of beta blockers include:

  • acebutolol (Sectral)
  • atenolol (Tenormin)
  • betaxolol (Kerlone)
  • bisoprolol (Zebeta)
  • carteolol (Cartrol)
  • labetalol (Normodyne, Trandate)
  • metoprolol (Lopressor, Toprol-XL)
  • nadolol (Corgard)
  • penbutolol (Levatol)
  • pindolol (Visken)
  • propranolol (Inderal)
  • sotalol (Betapace)
  • timolol (Blocadren)

Normally, the thyroid pulls the element iodine out of a person’s bloodstream so that it can be used to make hormones. When radioactive iodine is taken in liquid or pill form, the thyroid collects the iodine and, in treatment doses, the radioactivity destroys the gland. Typically, this treatment takes between six and 36 weeks to achieve its effect. People who receive this therapy will likely need to take thyroid hormone for the rest of their lives.

It is important that patients take thyroid medications exactly as prescribed by a physician. This helps ensure that treatment regimens are effective and safe. For example, patients who take one brand of thyroid hormone should not take another brand without a physician’s approval. The various brands of thyroid hormone contain different ingredients and can affect patients in different ways.


Conditions treated with thyroid medications

Antithyroid medications are prescribed to treat symptoms associated with a variety of thyroid conditions, including:

  • Hyperthyroidism. Results from overactivity of the thyroid gland, which secretes hormones that regulate a person’s metabolism (the physical and chemical processes necessary for the maintenance of life). Patients experience the release of too much thyroid hormone into the bloodstream, causing processes in the body to speed up. Symptoms include thyroid enlargement (goiter) and sudden, unexplained weight loss.

    The most common cause of hyperthyroidism is Graves’ disease, an autoimmune disorder. Some people with Graves’ disease may experience variations that affect the eyes (Graves’ ophthalmopathy) or the skin on the shins and the top of the feet (Graves’ dermopathy).

  • Thyroid nodules and tumors. Growth of tissue in the thyroid that is usually benign (noncancerous), but in some cases malignant (cancerous).
  • Thyroiditis. Inflammation of the thyroid gland. There are several types that may cause either hyperthyroidism or hypothyroidism. Although “subacute” thyroiditis can cause hyperthyroidism, in general neither propylthiouracil or methimazole is used to treat this type of condition. On the other hand, Hashimoto’s thyroiditis is a common cause of hypothyroidism.

Thyroid hormone medications may be used to treat hypothyroidism, and radioactive iodine therapy may be used to treat hyperthyroidism, thyroid cancer, goiter and thyroid nodules.

Conditions of concern with thyroid medications

Patients are urged to report any allergies to their physician. It is especially important that patients report allergies to pork or beef if they are considering taking desiccated animal thyroid.

Other conditions that may affect a patient’s ability to take thyroid medications include:

  • Arrhythmias (abnormal heart rhythms), atherosclerosis or other cardiovascular disease
  • Diabetes
  • Certain other endocrine diseases, such as unresolved Addison’s disease (adrenal insufficiency) or an underactive pituitary gland
  • Kidney disease, such as proteinuria, diabetic nephropathy or end-stage renal disease
  • Liver disease
  • Malabsorption diseases (e.g., celiac disease, lactose intolerance, cystic fibrosis, Whipple disease)
  • Osteoporosis
Side effects

Potential side effects of thyroid medications

Side effects associated with thyroid medications vary depending on the type of drug the patient is taking. About 5 percent of patients may have an allergic reaction to antithyroid medications, according to the American Association of Clinical Endocrinologists. Symptoms include yellow skin (jaundice), skin rash, hives, fever and joint pain. This is most likely to occur within the first six weeks of treatment and usually subsides within a couple of weeks after a patient stops using the medication.

Uncommonly, antithyroid medications can damage neutrophils, a type of white blood cell that helps eradicate bacteria. Patients who use these drugs and develop a sore throat, fever or other signs of infection are urged to seek immediate medical attention so they can have a blood test performed. This should be done before the patient takes the next dose of antithyroid medication.

Thyroid drugs are among the medications that can cause drug-induced lupus. Symptoms can include muscle and joint pain and swelling, fatigue, fever and painful inflammation around the lungs or heart. Drug-induced lupus typically resolves when the medication is discontinued. It is far less serious than systemic lupus erythematosus, a chronic autoimmune disorder.

Patients who take too much thyroid hormone may develop hyperthyroidism or other side effects, such as strain on the heart or osteoporosis. Patients who take too little are likely to experience continued hypothyroidism. In addition, patients who take thyroid hormone to try to suppress the growth of thyroid nodules or enlarged thyroid gland (goiter) may experience several side effects. These include irregular or fast heartbeat, chest pain and decreased bone density.

Radioactive iodine therapy initially cause a release of thyroid hormone into the bloodstream that may cause symptoms to worsen for a time after treatments begin. These symptoms may include neck tenderness, sore throat and signs of hyperthyroidism. However, over time they begin to reverse as the treatment takes effect.

Beta blockers can cause mild hyperglycemia in diabetic patients, and studies have found them to be a minor risk factor for diabetes. Depending on the type of beta blocker prescribed, patients may experience various side effects, such as slow heart rate (bradycardia), shortness of breath (dyspnea) or wheezing, dizziness or fainting.

Other side effects associated with thyroid medications can include:

  • Anxiety
  • Burning, tingling or other abnormal sensations
  • Diarrhea, stomach cramps or other gastrointestinal upset
  • Drowsiness
  • Fever
  • Flushing
  • Hair loss
  • Headache
  • Hyperactivity
  • Increased appetite (polyphagia)
  • Loss of taste or salty taste
  • Menstrual cycle changes
  • Mouth sores or throat infection
  • Muscle/joint pain or weakness
  • Nausea or vomiting
  • Rapid changes in mood (e.g., irritability)
  • Skin rash, itchiness or eruptions
  • Sleeping difficulties
  • Swelling (edema)
  • Tremor or shakiness
  • Weight loss

Drug interactions with thyroid medications

Certain drugs may interact poorly when taken with thyroid medications. Patients are urged to consult their physician before taking any additional prescriptions, over-the-counter medications, nutritional supplements or herbal medications.

Certain medications can alter the amount of thyroid hormone that a patient requires for the hormone to be effective. Such medications include birth control pills, estrogen, testosterone or other androgens, anticonvulsants (seizure medications), antidepressants and cholesterol drugs.

Other drugs that may interact with thyroid medications include:

  • Anticoagulants (drugs that hinder blood clotting)
  • Antihypertensives
  • Antidiabetic agents
  • Aspirin and other salicylates
  • Oral corticosteroids
  • Some heart drugs (e.g., digoxin)
  • Some HIV drugs (e.g., efavirenz)
  • Human growth hormone
  • Insulin

Symptoms of thyroid medication overdose

Patients exhibiting any of these symptoms should contact their physician immediately:

  • Breathing difficulties
  • Changes in menstrual periods
  • Coldness
  • Constipation
  • Dry, puffy skin
  • Headache
  • Listlessness or sleepiness
  • Muscle aches
  • Rapid or irregular heartbeat
  • Seizures
  • Swelling in the front of the neck
  • Unusual fatigue or weakness
  • Weight gain

Lifestyle considerations

Patients are urged to closely follow their physician’s recommendations for taking thyroid medications and to adjust their daily routine accordingly. For example, thyroid hormone is usually best taken on an empty stomach so that food does not affect absorption of the hormone. It also should be taken once daily, preferably at the same time every day.

Other thyroid medications are taken several times daily and in many cases should be taken with food. Patients are urged to discuss with a physician the proper way to take their thyroid medication.

How to use

Pregnancy use issues with thyroid medications

Women who are pregnant or breastfeeding should talk to their physician about whether or not to continue taking thyroid medications. Generally, it is important for women with certain thyroid conditions to continue to take thyroid hormone throughout their pregnancy. In many cases, a physician will recommend boosting dosage levels of thyroid hormone at this time, as normal thyroid function in the mother is important to a fetus’ good health.

However, pregnant women are not treated with radioactive iodine therapy. If other medications cannot be used, thyroid surgery may be recommended for pregnant patients with some forms of hyperthyroidism.

Some thyroid medications may pose potential dangers to the offspring of women who are pregnant or breastfeeding. For this reason, women are urged to consult their physician about the risks and benefits of using these medications.

Child use issues

Some thyroid medications are prescribed to children, but the safety and efficacy of others have not been established for pediatric use. For this reason, parents are urged to consult their child’s physician about the risks and benefits of allowing their child to use these medications.

When thyroid hormone is used in babies, it should not be given with store-bought liquid suspensions, as the hormone can deteriorate when dissolved, according to the American Association of Clinical Endocrinologists. Instead, it advises that babies should receive the hormone via a crushed tablet suspended in a teaspoon of liquid.

Elderly use issues

Thyroid medications can generally be used safely by older patients. However, dosage levels may need to be adjusted, as elderly patients are often more susceptible to a medication’s effects than younger adults.

Questions for your doctor

Patients may wish to ask their doctor the following questions about thyroid medications:
  1. Which thyroid medication do you suggest for my condition? Why?
  2. What are the alternative treatments available to me?
  3. What are the side effects and risks associated with this drug?
  4. What are the risks if I do not begin treatment?
  5. Will I have to stop taking other medications while I am on this drug?
  6. How soon after I start taking this drug should I begin to notice improvement?
  7. For how long will I be required to take this medication?
  8. What should I do if I miss a dose of my drug or take too much?
  9. If the drug is not effective for me, is there another thyroid medication I should try?
  10. Is this drug safe for me if I’m pregnant or breastfeeding?
  11. Is this drug safe for my child or elderly parent?

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