The term goiter means any enlargement of the thyroid gland. It
refers only to the size of the thyroid gland, not to how well
the thyroid gland is functioning. Therefore, a patient with a
goiter may have too little, too much, or the proper amount of
thyroid hormone. When the thyroid gland is uniformly enlarged,
it is called a diffuse goiter. When a goiter contains one or more
nodules, it is called a nodular goiter. A thyroid nodule is a
localized growth in or on the thyroid gland. When discussing goiters
and nodules, it is important to keep in mind that they are generally
not cancerous.
During the early stages of goiter development, most patients are
unaware that they have a goiter. Symptoms can develop slowly
over time as the goiter increases in size and presses on certain
parts of the neck. Symptoms can include:
Patients with a goiter and an underactive thyroid gland that produces
too little thyroid hormone can also have signs and symptoms of
hypothyroidism, such as feeling tired and sleepy, being cold all
the time, losing their hair, feeling "blue," having
difficulty concentrating, and finding it difficult to lose weight.
Likewise, patients with a goiter and an overactive thyroid gland
that produces too much thyroid hormone can also have the signs
and symptoms of hyperthyroidism, such as being nervous and irritable,
feeling hot all the time, sweating more than usual, having difficulty
sleeping, experiencing heart palpitations, and losing weight.
The leading cause of goiters worldwide is a lack of iodine in
the diet. Thyroid hormone contains molecules of iodine, and, when
there is not enough dietary iodine, a goiter and/or hypothyroidism
can develop. Iodine deficiency is rarely the cause of goiters
in North America because iodine is added to salt and other foods.
Instead, the most common causes of goiter are:
High levels of TSH associated with hypothyroidism
In addition to stimulating the thyroid gland to make thyroid hormone,
TSH (thyroid stimulating hormone) causes the thyroid gland to
grow. When there is not enough thyroid hormone in the body, the
pituitary gland will increase production of TSH in an attempt
to stimulate the thyroid gland to make more thyroid hormone. When
patients are hypothyroid, their thyroid gland cannot make enough
thyroid hormones, and the pituitary gland continues to produce
TSH. Therefore, because of this continued elevation of TSH, the
thyroid gland may enlarge.
Antibodies associated with Graves' disease
The antibodies associated with Graves' disease behave like TSH
and stimulate the thyroid follicular cells to grow and produce
thyroid hormone. However, production of these antibodies is not
controlled by the normal thyroid feedback system.
As a result, the thyroid gland is overstimulated and can become
enlarged.
Growths (nodules)
Although no one knows precisely what causes most thyroid nodules,
it has been observed that patients exposed to certain types of
radiation are more likely to develop one or more. Some nodules
are have the ability to make thyroid hormone independently of
the normal thyroid feedback mechanism and hyperthyroidism can
develop. Most nodules, however, do not make thyroid hormone. It
is important to determine the number of nodules involved. Even
though most thyroid nodules are not cancerous, 5% to 10% are and require
further evaluation.
Inflammation or infection of the thyroid gland
When the thyroid gland becomes inflamed or infected, white blood
cells (lymphocytes) gather in the thyroid gland and cause it to
enlarge. The most common form of thyroid inflammation is Hashimoto's
thyroiditis, the leading cause of hypothyroidism in this country.
Other types of thyroiditis, such as postpartum thyroiditis and
subacute thyroiditis, can also produce goiters.
Fluid-filled lumps (cysts)
Most thyroid cysts are formed when the tissue inside a nodule
breaks down into a liquid. These cysts are seldom cancerous.
A hormone produced during pregnancy
HCG, a hormone produced during pregnancy, is thought to cause
a slight enlargement of the thyroid gland even during a normal
pregnancy. There are uncommon conditions that can lead to the
overproduction of this hormone, resulting in abnormal growth of
the thyroid gland as well as hyperthyroidism.
During a physical examination, physicians will often begin by
looking at your neck to see if it appears swollen. In order
to determine if the thyroid gland is the source of the swelling,
physicians may ask you to swallow several times in
order to observe or feel the movement of the thyroid gland. By
gently pressing his or her fingers along your neck, your physician determines
the size and texture of the thyroid gland as well as if there
is tenderness. In some cases, he or she may detect the presence of
one or more thyroid nodules.
Laboratory tests that measure the amount of thyroid hormone and
TSH in the bloodstream will determine if the thyroid gland is
functioning properly or if you are either hypo- or hyperthyroid.
Your physician may also order laboratory tests to measure thyroid
antibodies that could be present with either Hashimoto's thyroiditis
or Graves' disease.
Thyroid ultrasound can be an important diagnostic tool in evaluating
goiters. This is a painless procedure that forms a picture of
the thyroid gland by bouncing sound waves off of it. In addition
to determining the size of a goiter, ultrasound can detect the
presence of thyroid nodules as well as their size and structure.
If the ultrasound demonstrates the presence of clinically significant
nodules, then further tests will be necessary to determine whether
the growth is cancerous.
For hypothyroid patients with a diffuse goiter
Treatment of a goiter is based on the results of the physical
examination and laboratory tests. If tests show that the
thyroid gland is not producing enough thyroid hormone, then thyroid
hormone replacement with levothyroxine is necessary to treat the
hypothyroidism. In addition to restoring the proper level of thyroid
hormones, levothyroxine will sometimes reduce the size of the
goiter.
For hyperthyroid patients with a diffuse goiter
If your test indicates too much thyroid hormone in your
system, you will be treated for hyperthyroidism with either antithyroid
drugs, radioactive iodine, or surgery. The size of a goiter usually
decreases when the hyperthyroidism is successfully treated. If you have
radioactive iodine or surgery, you may become hypothyroid
and need levothyroxine therapy.
For patients with normal thyroid function and a diffuse goiter
To determine which option is best for you if you have a goiter
and a normally functioning thyroid gland, your physician will take
several factors into consideration, such as:
If your thyroid gland is producing the proper amount of
thyroid hormone and there are no nodules present, the following
treatment options available:
Observation
Your physician may choose to observe you if your goiter
is small, does not cause discomfort, and does not interfere with
swallowing or breathing.
Levothyroxine
Your physicians may prescribe levothyroxine in order to
suppress the release of TSH and prevent further stimulation of
the thyroid gland. Although goiters do not usually decrease in
size because of this treatment, levothyroxine may prevent them
from becoming larger. Levothyroxine is also sometimes prescribed
for patients who have the antithyroid antibodies associated with
Hashimoto's thyroiditis but are not yet hypothyroid.)
Surgery
Patients who elect to have part or all of their thyroid gland
removed by surgery (thyroidectomy) generally do so because they
have a very large goiter that is either causing discomfort or
interfering with their swallowing or breathing. Your
overall health and the degree to which the symptoms are affecting
you will be carefully considered before surgery is recommended.
After surgery, levothyroxine treatment may be recommended to replace
thyroid hormone if the remaining thyroid gland can no longer produce
sufficient amounts.
Radioactive iodine
On rare occasions, some physicians may recommend radioactive iodine
treatment to reduce the size of large goiters. Unlike surgery,
hospitalization is usually not required for this treatment. However,
the degree to which the size of the goiter will be reduced is
not as predictable as with surgery.
EM Pharma's ThyroCare™ brochures were developed to promote
a greater understanding of thyroid disease and the diagnostic
and treatment options available. If you have, or suspect you have,
a thyroid disorder, your physician is in the best position to
advise and treat you. We encourage you to discuss your questions
and concerns with him or her. Signs and symptoms
Causes
Diagnosis
Treatment