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Alternative Names
primary hypothyroidism

Hypothyroidism is a condition in which the thyroid gland does not produce adequate amounts of thyroid hormone.

What is going on in the body?
The thyroid gland is a small endocrine gland located in the lower neck. It produces thyroid hormone under regulation by the brain and the pituitary gland. Thyroid hormone, which is released into the body, regulates multiple body functions. It is important in maintaining normal metabolism. Thyroid hormone also helps maintain normal cholesterol balance, heart function, and brain function. Almost every system of the body is affected by hypothyroidism.

What are the signs and symptoms of the disease?
Only subtle symptoms may occur early in the course of hypothyroidism. These may include: Some individuals may notice hair loss, dry skin, or nail changes. If left untreated, the symptoms of hypothyroidism will progress. This can lead to fluid retention around the eyes or legs.

Untreated hypothyroidism can also cause congestive heart failure, a condition in which a weakened heart is unable to pump enough blood to body organs. In severe cases, the brain itself is affected. The person can lose mental function and even go into a coma.

What are the causes and risks of the disease?
Hypothyroidism is most commonly caused by an autoimmune disorder. An autoimmune disorder is a condition in which the body produces antibodies that attack its own cells for no known reason. Hashimoto's thyroiditis is an example of an autoimmune disorder that attacks the thyroid gland. Over time, this makes the thyroid gland unable to produce normal amounts of thyroid hormone.

Some individuals have an overactive thyroid, a condition known as hyperthyroidism. Medications can be given to destroy a portion of an overactive thyroid. If too much medication is given, the person can develop low thyroid function, or hypothyroidism. Surgery to remove the thyroid gland in someone with a condition such as thyroid cancer can also cause hypothyroidism.

What can be done to prevent the disease?
There is no known way to prevent autoimmune disorders that cause hypothyroidism, such as Hashimoto's thyroiditis. Careful monitoring of medications used to treat an overactive thyroid can help prevent hypothyroidism caused by destruction of too much of the gland tissue.

How is the disease diagnosed?
Diagnosis of hypothyroidism begins with a complete history and physical examination. Blood tests are done, including thyroid function tests. An antibody titre blood test may be done to see if the hypothyroidism is caused by an autoimmune disorder.

What are the long-term effects of the disease?
The long-term effects of untreated hypothyroidism can be profound. Severe, prolonged hypothyroidism can lead to multiple abnormalities within any system of the body including heart, brain, and skin. Untreated hypothyroidism can cause heart disease, osteoporosis or thinning of the bones, and infertility in women. If left untreated for many years, severe hypothyroidism can eventually lead to death.

The findings of a recent study have shown that pregnant women with hypothyroidism have 4 times the risk of miscarriage in the second trimester than other women. If the hypothyroidism is not treated appropriately, it can lead to mental retardation in the child.

What are the risks to others?
Hypothyroidism is not contagious and poses no risk to others.

What are the treatments for the disease?
Generally, there is no way to reverse the damage done to the thyroid gland. The doctor will prescribe thyroid hormone, such as levothyroxine or thyroxine (T3), to be taken on a daily basis. The right dose of medication should resolve the signs and symptoms of hypothyroidism.

What are the side effects of the treatments?
If a person has had hypothyroidism for many years, the replacement of thyroid hormone may be started slowly and eventually increased to normal levels. Because the thyroid hormone medication is chemically identical to the body's thyroid hormone, side effects or allergic reactions to the medications are quite rare.

If too much thyroid hormone is given, the person may develop arrhythmias, or irregular heartbeats, and osteoporosis, or thinning of the bones.

What happens after treatment for the disease?
Treatment of hypothyroidism is lifelong.

How is the disease monitored?
The doctor will use periodic thyroid function tests to monitor the level of medication needed. These blood tests may initially be done every 6 to 8 weeks, until a normal level of thyroid is restored. After the right dose of medication is established, thyroid function tests may then be done every 6 to 12 months. Any new or worsening symptoms should be reported to the doctor.

Author: Bill Harrison, MD
Reviewer: HealthAnswers Australia Medical Review Panel
Editor: Dr David Taylor, Chief Medical Officer HealthAnswers Australia
Last Updated: 1/10/2001
Potential conflict of interest information for reviewers available on request

This website and article is not a substitute for independent professional advice. Nothing contained in this website is intended to be used as medical advice and it is not intended to be used to diagnose, treat, cure or prevent any disease, nor should it be used for therapeutic purposes or as a substitute for your own health professional's advice.  All Health and any associated parties do not accept any liability for any injury, loss or damage incurred by use of or reliance on the information.


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