Hypothyroidism

Hypothyroidism

Myxedema- Adult hypothyroidism

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

See also:

Chronic thyroiditis (Hashimoto's disease)

Subacute thyroiditis

Silent thyroiditis

Neonatal hypothyroidism

Causes, incidence, and risk factors

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 pregnancy (often referred to as "postpartum thyroiditis").

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 cause hyperthyroidism and is often followed by temporary or permanent hypothyroidism

Certain drugs can cause hypothyroidism, 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

Symptoms

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

Signs and tests

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:

TSH test

T4 test

Lab tests may also reveal:

Anemia on a complete blood count (CBC)

Increased cholesterol levels

Increased liver enzymes

Increased prolactin

Low sodium

Treatment

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 possible that effectively relieves symptoms and brings your 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 thyroid medicine. Talk with your doctor if you are eating a lot of soy products or are on a high-fiber diet.

Thyroid medicine works best on an empty stomach and when taken 1 hour before any other medications.

Do NOT take thyroid hormone with fiber supplements, calcium, iron, multivitamins, aluminum hydroxide antacids, colestipol, or medicines that bind bile acids.

After you start taking replacement therapy, tell your doctor if you have any symptoms of increased thyroid activity (hyperthyroidism) such as:

Palpitations

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.

Expectations (prognosis)

In most cases, thyroid levels return to normal with proper treatment. However, thyroid hormone replacement must be taken for the rest of your life.

Myxedema coma can result in death.

Complications

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).

Calling your health care provider

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

Prevention

There is no prevention for hypothyroidism.

Screening tests in newborns can detect hypothyroidism that is present from birth (congenital hypothyroidism).