Hyperthyroidism and Hypothyroidism

The thyroid is a butterfly-shaped gland in the neck. It produces thyroid hormone, which helps control your body’s energy use (metabolism). Sometimes, the thyroid either works too hard (overactive) or not hard enough (underactive) at producing its hormone because of disease. An estimated 27 million Americans have thyroid disease, and about half have never been diagnosed.

An overactive thyroid gland is called hyperthyroidism. Graves’ disease is a type of hyperthyroidism that occurs when the immune system attacks the thyroid gland and causes it to produce too much of its hormones.

An underactive thyroid gland is called hypothyroidism. Hashimoto’s disease is a form of hypothyroidism in which the body attacks the thyroid gland and causes it to produce too few of its hormones.

Sometimes a thyroid problem will cause the gland to become larger. This is called a goiter. The thyroid gland can also develop growths. Non-cancerous growths are called nodules. Less commonly, growths can be cancerous.

Causes
Causes of hypothyroidism:
The most common cause of hypothyroidism worldwide is iodine deficiency, because the thyroid needs iodine in order to produce its hormones. In the United States, where iodine deficiency is not usually a problem, causes may include:

• Hashimoto’s disease
• Medications, such as lithium
• Pregnancy
• Surgical removal of the thyroid (thyroidectomy)
• Treatment for hyperthyroidism

Causes of hyperthyroidism:

• Graves’ disease
• Thyroid nodules that produce too much thyroid hormone
• Thyroiditis (swollen and inflamed thyroid gland)

Risk Factors
Risk factors for hypothyroidism:

• A close relative (such as a grandparent) with the condition
• Female gender
• Obesity
• Radiation to the head or neck
• Thyroid surgery (thyroidectomy)
• Treatment for hyperthyroidism (with anti-thyroid medications)

Risk factors for thyroid cancer:

• Age between 20 and 60
• Diet low in iodine (more common in other parts of the world)
• Female gender
• Inheriting an abnormal gene
• Previous radiation to the head and neck

Symptoms
Symptoms of hyperthyroidism:

• A lump (goiter) in the neck
• Anxiety
• Bulging eyes (Graves’ disease)
• Difficulty sleeping
• Excessive sweating
• Tremor in the hands and fingers
• More frequent bowel movements
• Fast or irregular heartbeat
• Increased sensitivity to heat
• Nervousness
• Weight loss, despite eating normally

Symptoms of hypothyroidism:

• A lump (goiter) in the neck
• Constipation
• Difficulty concentrating
• Difficulty swallowing
• Dry skin
• Fatigue
• Hair loss
• Intolerance to cold
• Irregular menstrual periods
• Weight gain despite normal eating habits

Symptoms of thyroid cancer:

• Breathing problems
• Difficulty swallowing
• Hoarseness or other voice change
• Lump or swelling in the neck that may grow rapidly in size
• Pain the front of the neck
• Enlarged lymph nodes under your jaw or neck

Diagnosis
When your doctor suspects a thyroid problem, he will take a medical history and perform a physical examination. Specifically, the doctor will examine your neck for any lumps or nodules in the area of the thyroid gland.

Other tests may include:

• Blood tests to check if thyroid hormone levels are abnormally high or low
• Thyroid antibody blood tests to detect antibodies against the thyroid gland (to check for the presence of an autoimmune condition such as Graves’ disease)
• Ultrasound of the neck
• Chest x-ray
• Computed tomography (CT) or magnetic resonance imaging (MRI) scan
• Radioactive iodine uptake test to see how well the thyroid is taking up iodine (which it uses to make its hormone).  This test is rarely performed today

Treatment
Treatments for thyroid disease vary based on the type of condition.

Hyperthyroidism treatments

• Anti-thyroid medications, such as methimazole or propylthiouracil (PTU), to lower the amount of hormone produced by the thyroid
• Beta-blocker medications, to control rapid heart rate, anxiety, and other symptoms of overactive thyroid
• Radioactive iodine is taken as a pill.  It works by destroying the thyroid gland

If medication alone is not enough to treat the problem, your doctor may remove part of your thyroid gland (thyroidectomy). There is always a risk of damaging the delicate parathyroid glands and nerves to the larynx (voice box) while performing this surgery, but using careful monitoring techniques during the surgery can reduce the risks.

Hypothyroidism treatments

• Thyroid hormone medication (levothyroxine sodium) to replace what your body isn’t producing

Goiter treatments
If the goiter is small and isn’t causing you any discomfort, the doctor may just wait and watch it for signs of growth. For a goiter that is causing problems, treatments may include:

• Radioactive iodine to destroy the thyroid gland
• Suppression therapy with thyroid hormone to shrink the goiter
• Surgery to remove all or part of the thyroid gland (partial or total thyroidectomy)

If the thyroid is removed by surgery or destroyed by radioactive iodine, you will need to take daily thyroid hormone pills for the rest of your life

Thyroid cancer treatments
Thyroid cancer is one of the least deadly cancers, with a five-year survival rate of about 97 percent. Treatments include:

• Surgery to remove the lobe containing the cancer (lobectomy) or part or all of the thyroid gland (thyroidectomy)
• Radioactive iodine therapy to destroy any cancer not removed during surgery
• External-beam radiation

Prognosis
Thyroid conditions can respond well to treatment. However, if they are left untreated, both overactive and underactive thyroid can lead to complications.

Complications of hypothyroidism include:

• Birth defects in babies born to mothers with the condition
• Depression
• Goiter
• Heart problems (including an enlarged heart and heart failure)
• Myxedema coma (a rare and life-threatening condition)

Complications of hyperthyroidism include:

• Bulging, swollen eyes and other eye problems
• Decreased sexual desire
• Depression
• Heart problems (including rapid heart rate)
• Osteoporosis
• Slowed mental functioning

It’s especially important to treat thyroid problems during pregnancy, because they can lead to miscarriage, intrauterine growth restriction, preeclampsia (high blood pressure in the mother), and premature birth.  

Sources:
The Hormone Foundation. Graves’ Disease.
http://www.hormone.org/Resources/Thyroid/upload/bilingual_GravesDisease.pdf
The Hormone Foundation. Hashimoto’s Disease.
http://www.hormone.org/Resources/Thyroid/upload/Bilingual_Hashimotos_Disease.pdf
Kronenberg HM, Melmed S, Polonsky KS, Larsen PR. Kronenberg: Williams Textbook of Endocrinology. 11th ed. Philadelphia, PA: Saunders Elsevier; 2008.
Neale DM, Cootauco AC, Burrow G. Thyroid Disease in Pregnancy. Clinics in Perinatology. 2007;34:543-557.
American Cancer Society. Thyroid Cancer.
http://www.cancer.org/docroot/CRI/content/CRI_2_4_1X_What_is_thyroid_cancer_43.asp?rnav=cri