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What is hypothyroidism?

Hypothyroidism is a condition in which the thyroid gland does not make enough thyroid hormone. Too little hormone slows down chemical reactions in the body. This slowdown causes mental and physical changes.

The thyroid gland is located in the lower front of the neck. This gland takes iodine from the food you eat to make hormones called thyroxine (T4) and triiodothyronine (T3). The hormones control your metabolism (the chemical processes your body uses to turn the food you eat into energy). You need thyroid hormones to control body temperature, heart rate, appetite, and digestion. If you have too little hormone, you may gain weight, your body temperature may get lower, and you may feel tired or sluggish.

How does it occur?

Some of the more common causes of hypothyroidism are:

  • Hashimoto's disease (thyroiditis): This condition is an irritation and swelling of the thyroid gland. It is caused by a problem with the immune system. The immune system is your body's protection against infection, but sometimes it sees your own body as foreign and reacts to it.
  • Complete or partial removal of the thyroid gland with surgery.
  • Viruses: They can infect the thyroid gland and cause it to make too little hormone.
  • Radiation: Radioactivity can destroy the thyroid gland and its ability to make thyroid hormone. Radioactive iodine is a common treatment for an overactive thyroid gland, but often the treatment leads to an underactive thyroid gland. Also, X-ray treatment for cancer of the head or neck may expose the thyroid gland to radiation and damage it.
  • Overdosage of medicine used to treat hyperthyroidism.

Anyone can have hypothyroidism, but it happens most often in women over age 40. Some thyroid problems are inherited. Some are present at birth.

What are the symptoms?

The slowing of your body's processes can take months or even years. This can make it hard to know that this disease is causing your problems.

Symptoms of hypothyroidism include:

  • tiredness
  • depression
  • muscle weakness
  • constipation
  • weight gain
  • feeling cold a lot of the time
  • heavy and long menstrual periods
  • coarse, dry hair
  • early graying of hair in young adults
  • thick, dry skin
  • swollen eyelids
  • deep, hoarse voice
  • thick tongue
  • thickened facial features
  • slowed heart rate
  • less interest in sex
  • loss of hearing
  • numb and tingling hands.

A condition that develops after several years of untreated hypothyroidism is called myxedema. Myxedema can cause you to feel cold, be slow to talk and move, be less mentally alert, and possibly feel drowsy much of the time. You can even fall into a coma.

How is it diagnosed?

Your healthcare provider will ask about your symptoms and examine you. Blood tests can measure the levels of thyroid hormone. They can also measure thyroid-stimulating hormone (TSH) made by your pituitary gland. TSH causes your thyroid gland to make thyroid hormone.

How is it treated?

Your healthcare provider will prescribe synthetic thyroid hormone medicine. You will most likely need to take the medicine every day for the rest of your life.

Most people need only small doses of the thyroid medicine. After starting treatment, you will have more blood tests to be sure you are taking the right amount of thyroid hormone. It may take several weeks to find the right dosage for you. Once the correct dosage is found, your thyroid hormone level will need to be checked every few months.

If you have coronary artery disease or are at risk for it, your provider will prescribe a smaller dose of hormone at first. Replacing thyroid hormone too quickly can be hard on your heart. In some cases it can trigger a heart attack. Taking too much thyroid hormone can also cause osteoporosis.

For all of these reasons your thyroid hormone blood level will be checked for the rest of your life to make sure it is in the correct, normal range.

How long will the effects last?

Usually hypothyroidism starts getting better within a week after you start hormone therapy. All symptoms go away in a few weeks. In most cases, however, you must continue this treatment for the rest of your life.

Mild hypothyroidism may cause no symptoms. Without treatment, however, the disease can become disabling over time. Untreated hypothyroidism may cause the following problems:

  • slowing of mental processes
  • loss of consciousness.
  • enlargement of the heart and heart failure (rare)

If the cause of hypothyroidism is thyroiditis and it is not treated, your thyroid gland may swell. This swelling, called a goiter, may cause a big bulge in your neck.

How can I take care of myself?

If you are an older adult with hypothyroidism, you may not get medical treatment because you don't know you have a problem that can be treated. You may think your symptoms are just part of aging. If you have symptoms such as tiredness, muscle weakness, dry skin, depression, feeling cold, and constipation, see your healthcare provider.

When you have hypothyroidism, be sure to:

  • Follow your provider's instructions for taking your medicine.
  • Get your thyroid hormone level checked as often as your provider suggests.
  • Keep your follow-up appointments.
  • See your healthcare provider if any of your symptoms are not getting better or they come back.
  • See your healthcare provider if you have new symptoms.

How can I help prevent hypothyroidism?

In most cases hypothyroidism cannot be prevented.

Developed by RelayHealth.
Published by RelayHealth.
Last modified: 2011-06-02
Last reviewed: 2011-02-01
This content is reviewed periodically and is subject to change as new health information becomes available. The information is intended to inform and educate and is not a replacement for medical evaluation, advice, diagnosis or treatment by a healthcare professional.
© 2011 RelayHealth and/or its affiliates. All rights reserved.
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