The thyroid gland is located in the front of the neck, just below the voice box (larynx). It produces chemicals (hormones) that help the body control metabolism. Thyroid hormone is also produced in response to another hormone released by the pituitary gland.
There are four main types of thyroid disease:
•    Hyperthyroidism -- too much thyroid hormone
•    Hypothyroidism -- too little thyroid hormone
•    Benign (non-cancerous) thyroid disease
•    Thyroid cancer

Hyperthyroidism is a condition in which the thyroid gland makes too much thyroid hormone. The condition is often referred to as an "overactive thyroid."

The thyroid gland is an important organ of the endocrine system. It is located in the front of the neck just below the voice box. The gland produces the hormones thyroxine (T4) and triiodothyronine (T3), which control the way every cell in the body uses energy. This process is called yourmetabolism.
Hyperthyroidism occurs when the thyroid releases too much of its hormones over a short (acute) or long (chronic) period of time. Many diseases and conditions can cause this problem, including:

•    Getting too much iodine
•    Graves disease (accounts for most cases of hyperthyroidism)
•    Inflammation (thyroiditis) of the thyroid due to viral infections or other causes
•    Noncancerous growths of the thyroid gland or pituitary gland
•    Taking large amounts of thyroid hormone
•    Tumors of the testes or ovaries

•    Difficulty concentrating
•    Fatigue
•    Frequent bowel movements
•    Goiter (visibly enlarged thyroid gland) or thyroid nodules
•    Heat intolerance
•    Increased appetite
•    Increased sweating
•    Irregular menstrual periods in women
•    Nervousness
•    Restlessness
•    Weight loss (rarely, weight gain)

Other symptoms that can occur with this disease:
•    Breast development in men
•    Clammy skin
•    Diarrhea
•    Hair loss
•    Hand tremor
•    Weakness
•    High blood pressure
•    Itching - overall
•    Lack of menstrual periods in women
•    Nausea and vomiting
•    Pounding, rapid, or irregular pulse
•    Protruding eyes (exophthalmos)
•    Rapid, forceful, or irregular heartbeat (palpitations)
•    Skin blushing or flushing
•    Sleeping difficulty

Physical examination may reveal thyroid enlargement, tremor, hyperactive reflexes, or an increased heart rate. Systolic blood pressure (the first number in a blood pressure reading) may be high.
Subclinical hyperthyroidism is a mild form of hyperthyroidism that is diagnosed by abnormal blood levels of thyroid hormones, often in the absence of any symptoms.
Blood tests are also done to measure levels of thyroid hormones.

•    TSH (thyroid stimulating hormone) level is usually low
•    T3 and free T4 levels are usually high

This disease may also affect the results of the following tests:
•    Cholesterol test
•    Glucose test
•    Radioactive iodine uptake
•    T3RU
•    Triglycerides

How the condition is treated depends on the cause and the severity of symptoms. Hyperthyroidism is usually treated with one or more of the following:

•    Antithyroid medications
•    Radioactive iodine (which destroys the thyroid and stops the excess production of hormones)
•    Surgery to remove the thyroid

If the thyroid must be removed with surgery or destroyed with radiation, you must take thyroid hormone replacement pills for the rest of your life.

Beta-blockers such as propranolol are used to treat some of the symptoms, including rapid heart rate, sweating, and anxiety until the hyperthyroidism can be controlled.

Thyroid crisis (storm), also called thyrotoxicosis, is a sudden worsening of hyperthyroidism symptoms that may occur with infection or stress. Fever, decreased mental alertness, and abdominal pain may occur. Immediate hospitalization is needed.
Other complications related to hyperthyroidism include:

•    Heart-related complications including:
o    Rapid heart rate
o    Congestive heart failure
o    Atrial fibrillation
•    Increased risk for osteoporosis, if hyperthyroidism is present for a long time
•    Surgery-related complications, including:
o    Scarring of the neck
o    Hoarseness due to nerve damage to the voice box
o    Low calcium level due to damage to the parathyroid glands (located near the thyroid gland)
•    Treatments for hypothyroidism, such as radioactive iodine, surgery, and medications to replace thyroid hormones can have complications.

Precautions and Preventions
There are no known ways to prevent hyperthyroidism.

Call your health care provider if you have following symptoms that could be caused by too much thyroid hormone production.
•    Change in consciousness
•    Dizziness
•    Rapid, irregular heartbeat
Call your health care provider if you are being treated for hyperthyroidism and you develop symptoms of underactive thyroid, including:
•    Depression
•    Mental and physical sluggishness
•    Weight gain

Hypothyroidism is a condition in which the thyroid gland does not make enough thyroid hormone.

The thyroid gland is located in the front of the neck just below the voice box (larynx). It releases hormones that control metabolism.
The most common cause of hypothyroidism is inflammation of the thyroid gland, which damages the gland's cells. Autoimmune or Hashimoto's thyroiditis, in which the immune system attacks the thyroid gland, is the most common example of this. Some women develop hypothyroidism after pregancy (often referred to as "postpartum throiditis").

Other common causes of hypothyroidism include:
•    Congenital (birth) defects
•    Radiation treatments to the neck to treat different cancers, which may also damage the thyroid gland
•    Radioactive iodine used to treat an overactive thyroid (hyperthyroidism)
•    Surgical removal of part or all of the thyroid gland, done to treat other thyroid problems
•    Viral thyroiditis, which may case hyperthyroidism and is often followed by temporary or permanent hypothyroidism

Certain drugs can cause hyperthyroidism, including:
•    Amiodarone
•    Drugs used for hyperthyroidism (overactive thyroid), such as propylthiouracil (PTU) and methimazole
•    Lithium
•    Radiation to the brain
•    Sheehan syndrome, a condition that may occur in a woman who bleeds severely during pregnancy or childbirth and causes destruction of the pituitary gland

Risk factors include:
•    Age over 50 years
•    Being female

Early symptoms:

•    Being more sensitive to cold
•    Constipation
•    Depression
•    Fatigue or feeling slowed down
•    Heavier menstrual periods
•    Joint or muscle pain
•    Paleness or dry skin
•    Thin, brittle hair or fingernails
•    Weakness
•    Weight gain (unintentional)
Late symptoms, if left untreated:

•    Decreased taste and smell
•    Hoarseness
•    Puffy face, hands, and feet
•    Slow speech
•    Thickening of the skin
•    Thinning of eyebrows

A physical examination may reveal a smaller-than-normal thyroid gland, although sometimes the gland is normal size or even enlarged (goiter). The examination may also reveal:
•    Brittle nails
•    Coarse facial features
•    Pale or dry skin, which may be cool to the touch
•    Swelling of the arms and legs
•    Thin and brittle hair
A chest x-ray may show an enlarged heart.
Laboratory tests to determine thyroid function include:
•    Serum TSH
•    T4 test
Lab tests may also reveal:
•    Anemia on a complete blood count (CBC)
•    Increased cholesterol levels
•    Increased liver enzymes
•    Increased prolactin
•    Low sodium

The purpose of treatment is to replace the thyroid hormone that is lacking. Levothyroxine is the most commonly used medication. Doctors will prescribe the lowest dose that effectively relieves symptoms and brings the TSH level to a normal range. If you have heart disease or you are older, your doctor may start with a very small dose.

Lifelong therapy is required unless you have a condition called transient viral thyroiditis.
You must continue taking your medication even when your symptoms go away. When starting your medication, your doctor may check your hormone levels every 2 - 3 months. After that, your thyroid hormone levels should be monitored at least every year.

Important things to remember when you are taking thyroid hormone are:
•    Do NOT stop taking the medication when you feel better. Continue taking the medication exactly as directed by your doctor.
•    If you change brands of thyroid medicine, let your doctor know. Your levels may need to be checked.
•    Some dietary changes can change the way your body absorbs the thryoid medicine. Talk with your doctor if you are eating a lot of soy products or a high-fiber diet.
•    Thryoid medicine works best on an empty stomach and when taken 1 hour before any other medications. Do NOT take thyroid hormone with calcium, iron, multivitamins, alumin hydroxide antacids, colestipol, or other medicines that bind bile acids, or fiber supplements.
After you start taking replacement therapy, tell your doctor if you have any symptoms of increased thyroid activity (hyperthyroidism) such as:

•    Rapid weight loss
•    Restlessness or shakiness
•    Sweating

Myxedema coma is a medical emergency that occurs when the body's level of thyroid hormones becomes extremely low. It is treated with intravenous thyroid hormone replacement and steroid medications. Some patients may need supportive therapy (oxygen, breathing assistance, fluid replacement) and intensive-care nursing.

Myxedema coma, the most severe form of hypothyroidism, is rare. It may be caused by an infection, illness, exposure to cold, or certain medications in people with untreated hypothyroidism.
Symptoms and signs of myxedema coma include:

•    Below normal temperature
•    Decreased breathing
•    Low blood pressure
•    Low blood sugar
•    Unresponsiveness
Other complications are:

•    Heart disease
•    Increased risk of infection
•    Infertility
•    Miscarriage
People with untreated hypothyroidism are at increased risk for:

•    Giving birth to a baby with birth defects
•    Heart disease because of higher levels of LDL ("bad") cholesterol
•    Heart failure
People treated with too much thyroid hormone are at risk for angina or heart attack, as well as osteoporosis (thinning of the bones).

There is no prevention for hypothyroidism.
Screening tests in newborns can detect hypothyroidism that is present from birth (congenital hypothyroidism).

Call your health care provider if you have symptoms of hypothyroidism (or myxedema).

If you are being treated for hypothyroidism, call your doctor if:

• You develop chest pain or rapid heartbeat
• You have an infection
• Your symptoms get worse or do not improve with treatment

You develop new symptoms

A goiter is an enlargement of the thyroid gland. It is not cancer.

There are different kinds of goiters. A simple goiter can occur for no known reason, or when the thyroid gland is not able to produce enough thyroid hormone to meet the body's needs. The thyroid gland makes up for this by becoming larger.

There are two types of simple goiter:
•    Endemic (colloid) goiter
•    Sporadic (nontoxic) goiter

Colloid goiters occur in groups of people who live in areas with iodine-poor soil. These regions are usually away from the sea coast. People in these communities might not get enough iodine in their diet (iodine is needed to produce thyroid hormone).
The use of iodized table salt prevents iodine deficiency. In most cases of sporadic goiter the cause is unknown. Occasionally, certain medications such as lithium or aminoglutethimide can cause a nontoxic goiter.

Inherited factors may cause goiters. Risk factors include:
•    Age over 40 years
•    Family history of goiter
•    Female gender
•    Not getting enough iodine in the diet

The main symptom is a swollen thyroid gland. The size may range from a single small nodule to a large neck lump.

The swollen thyroid can put pressure on the windpipe and esophagus, which can lead to:
•    Cough
•    Hoarseness
•    Swallowing difficulties
•    Breathing difficulties (may rarely occur with very large goiters)
There may be neck vein swelling and dizziness when the arms are raised above the head.

The doctor will feel your neck as you swallow. The doctor may be able to feel swelling in the area.
Tests that may be done include:
•    Free thyroxine (T4)
•    Thyroid scan and uptake
•    Thyroid stimulating hormone (TSH)
•    Ultrasound of thyroid
If nodules are found on ultrasound, a biopsy should be done to check for thyroid cancer.