Disease In Focus: Goiter
Goiter is an abnormal enlargement of your thyroid gland. Your thyroid is a butterfly-shaped gland located at the base of your neck just below
your Adam's apple. Although goiters are usually painless, a large goiter can cause a cough and make it difficult for you to swallow or breathe.The most
common cause of goiter worldwide is a lack of iodine in the diet. In the United
States, where the use of iodized salt is common, a goiter is more often due to
the over- or underproduction of thyroid hormones or to nodules that develop in
the gland itself.
Treatment
depends on the size of the goiter, your symptoms and the underlying cause.
Small goiters that aren't noticeable and don't cause problems usually don't
need treatment.
SYMPTOMS
Not all
goiters cause signs and symptoms. When signs and symptoms do occur they may
include:
- A visible swelling at the base of your neck that
may be particularly obvious when you shave or put on makeup
- A tight feeling in your throat
- Coughing
- Hoarseness
- Difficulty swallowing
- Difficulty breathing
CAUSES
Your
thyroid gland produces two main hormones — thyroxine (T-4) and triiodothyronine
(T-3).
These
hormones circulate in your bloodstream and help regulate your metabolism. They
maintain the rate at which your body uses fats and carbohydrates, help control
your body temperature, influence your heart rate, and help regulate the
production of proteins. Your thyroid gland also produces calcitonin — a hormone
that helps regulate the amount of calcium in your blood.
Your
pituitary gland and hypothalamus control the rate at which these hormones are
produced and released.
The
process begins when the hypothalamus — an area at the base of your brain that
acts as a thermostat for your whole system — signals your pituitary gland to
make a hormone known as thyroid-stimulating hormone (TSH). Your pituitary gland
— also located at the base of your brain — releases a certain amount of TSH,
depending on how much thyroxine and T-3 are in your blood. Your thyroid gland,
in turn, regulates its production of hormones based on the amount of TSH it
receives from the pituitary gland.
Having a
goiter doesn't necessarily mean that your thyroid gland isn't working normally.
Even when it's enlarged, your thyroid may produce normal amounts of hormones. It
might also, however, produce too much or too little thyroxine and T-3.
A number
of factors can cause your thyroid gland to enlarge. Among the most common are:
Iodine deficiency. Iodine, which is essential for
the production of thyroid hormones, is found primarily in seawater and in the
soil in coastal areas. In the developing world, people who live inland or at
high elevations are often iodine deficient and can develop goiter when the
thyroid enlarges in an effort to obtain more iodine. The initial iodine
deficiency may be made even worse by a diet high in hormone-inhibiting foods,
such as cabbage, broccoli and cauliflower.
Although a
lack of dietary iodine is the main cause of goiter in many parts of the world,
this is not often the case in countries where iodine is routinely added to
table salt and other foods.
Graves' disease. Goiter can sometimes occur when
your thyroid gland produces too much thyroid hormone (hyperthyroidism). In
Graves' disease, antibodies produced by your immune system mistakenly attack
your thyroid gland, causing it to produce excess thyroxine. This
overstimulation causes the thyroid to swell.
Hashimoto's disease. Goiter can also result from an
underactive thyroid (hypothyroidism). Like Graves' disease, Hashimoto's disease
is an autoimmune disorder. But instead of causing your thyroid to produce too
much hormone, Hashimoto's damages your thyroid so that it produces too little.
Sensing a
low hormone level, your pituitary gland produces more TSH to stimulate the
thyroid, which then causes the gland to enlarge.
Multinodular goiter. In this condition, several solid or
fluid-filled lumps called nodules develop in both sides of your thyroid,
resulting in overall enlargement of the gland.
Solitary thyroid nodules. In this case, a single nodule
develops in one part of your thyroid gland. Most nodules are noncancerous
(benign) and don't lead to cancer.
Thyroid cancer. Thyroid cancer is far less common
than benign thyroid nodules. Cancer of the thyroid often appears as an
enlargement on one side of the thyroid.
Pregnancy. A hormone produced during
pregnancy, human chorionic gonadotropin (HCG), may cause your thyroid gland to
enlarge slightly.
Inflammation. Thyroiditis is an inflammatory
condition that can cause pain and swelling in the thyroid. It may also cause an
over- or underproduction of thyroxine.
RISK FACTORS
Goiters
can affect anyone. They may be present at birth and occur at any time
throughout life, although they're more common after age 40. Some common risk
factors for goiter include:
A
lack of dietary iodine.
People living in areas where iodine is in short supply and who don't have
access to iodine supplements are at high risk of goiter.
Being
female. Because women
are more prone to thyroid disorders, they're also more likely to develop
goiters.
Your
age. Your chances of
developing a goiter increase with age.
Medical
history. A personal or
family history of autoimmune disease increases your risk.
Pregnancy
and menopause. For
reasons that aren't entirely clear, thyroid problems are more likely to occur
during pregnancy and menopause.
Certain
medications. Some
medical treatments, including immunosuppressants, antiretrovirals, the heart
drug amiodarone (Cordarone, Pacerone, others) and the psychiatric drug lithium
(Lithobid, others), increase your risk.
Radiation
exposure. Your risk
increases if you've had radiation treatments to your neck or chest area or
you've been exposed to radiation in a nuclear facility, test or accident.
COMPLICATIONS
Small
goiters that don't cause physical or cosmetic problems aren't a concern. But
large goiters can make it hard to breathe or swallow and can cause a cough and
hoarseness. Goiters that result from other conditions, such as hypothyroidism
or hyperthyroidism, can be associated with a number of symptoms, ranging from
fatigue and weight gain to unintended weight loss, irritability and trouble
sleeping.
If your
goiter is caused by your diet, these suggestions can help:
Get
enough iodine. To
ensure that you get enough iodine, use iodized salt or eat seafood or seaweed —
sushi is a good seaweed source — about twice a week. Shrimp and other shellfish
are particularly high in iodine. If you live near the coast, locally grown
fruits and vegetables are likely to contain some iodine, too, as are cow's milk
and yogurt.
Everyone
needs about 150 micrograms of iodine a day (the amount in slightly less than
half a teaspoon of iodized salt). But adequate amounts are especially important
for pregnant and lactating women and for infants and children.
Reduceiodine consumption.
Although it's uncommon, getting too much iodine sometimes leads to goiter. If
excess iodine is a problem, avoid iodine-fortified salt, shellfish, seaweed and
iodine supplements.