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The Thyroid Gland

The thyroid gland is part of the endocrine system within the body. The endocrine system
refers to special organs or glands that make hormones. Hormones work as chemical
messengers in the body. One of the most well known endocrine organs is the pancreas,
which makes insulin, a chemical messenger, which targets cells throughout the body to
metabolize blood sugar. Other common endocrine glands include the pituitary,
parathyroids, and adrenal glands.

The thyroid gland is located in the front of the lower neck. It is made up of two lobes, the
right and left lobe, connected by a thin band of tissue called the isthmus. This structure
gives the thyroid gland the appearance of a butterfly overlying the neck below the thyroid
cartilage (Adam’s apple).

Understanding the role of the thyroid and metabolism aids in understanding certain
thyroid diseases. Hypothyroidism results when the thyroid gland is underactive. This is
the most common thyroid disease. Hypothyroidism causes a decrease in the body’s
metabolic rate and can result in symptoms such as weight gain, decreased heart rate,
and feeling cold. Hyperthyroidism results from an overactive thyroid gland and can give
the sensation of nervousness, increased heart rate, shaky hands, and weight loss.
Euthyroid is the term used to describe normal thyroid function.

Thyroid Diseases
Thyroid diseases are very common. The most common thyroid diseases are those
associated with abnormal gland activity: hypothyroidism and hyperthyroidism as
described in the above sections. Two other types of thyroid diseases are an enlargement
in the size of the gland or lumps and nodules within the gland. Often, in both of these
diseases, the thyroid gland continues to function at normal activity.
Thyroid Gland Enlargement
An enlargement of the thyroid gland is called a goiter. In some areas of the world iodine
deficiency is related to goiters. In the US, iodine deficiency is not a common problem
and usually not the cause of enlargement. Thyroid function may or may not be altered
with gland enlargement. The enlarged gland, however, can cause pressure on other
structures in the neck, primarily the esophagus (swallowing tube) and trachea (breathing
tube). Gland enlargement can also become cosmetically less than desirable. It is often
for these reasons that surgery is recommended.

Thyroid Nodules
A nodule is a lump within the gland. Nodules are present in approximately one of every
15 women and one in 60 men in the United States. Ultrasound testing of the neck will
usually show more than one nodule within the thyroid gland. Most thyroid nodules are
not cancers and do not cause any health problems. Testing some of the fluid or cells
from the nodule can sometimes help to determine if the nodule is a cancer. This test is
called a fine needle aspiration and can be done either in radiology or the doctor’s office.
Unfortunately, this test is not always able to determine if the nodule is benign and
surgery may be recommended. Usually, the surgeon removes the thyroid lobe, which
enables the pathologist to examine the entire nodule and lobe for a definitive diagnosis.
Thyroid nodules are more likely to be cancerous if only one nodule is found.

Thyroid Cancer
Thyroid cancer grows slowly and it may take years before it causes problems. Thyroid
cancer accounts for only 0.4% of all cancer deaths. The outlook for people with this
disease is very good. Thyroid cancer usually causes a small growth in the thyroid gland
rather than enlargement of the whole gland. Most often the disease is curable with
surgery and follow-up treatment. There are 4 main types of thyroid cancers. Papillary
carcinoma is the most common and usually occurs in younger individuals. Papillary
carcinoma accounts for 60.7% of all thyroid cancers. Follicular carcinoma is less
common and occurs in older persons. Medullary is a rare form of thyroid cancer that
tends to run in families. Anaplastic is the rarest form of thyroid cancer and tends to grow
more quickly.

The initial treatment for thyroid cancer is surgery to remove the entire gland. Even if the
tumor is small the entire gland is usually removed to facilitate treatment with radioactive
iodine approximately 4 weeks after surgery. If radioactive iodine treatment is planned for
thyroid cancer; thyroid medication is not given until the treatment is completed.

Thyroid Surgery
Surgery is a treatment for certain thyroid diseases. Surgery can be done to remove
thyroid nodules, an enlarged thyroid gland, and to remove a thyroid gland or nodules
that are overactive. Thyroid surgery usually entails a one-night stay in the hospital. The
Medical College of Wisconsin has a dedicated team of health care professionals
specializing in endocrine surgery. Endocrine surgeons with special expertise and
training, as well as membership in the American Association of Endocrine Surgeons are
a key part of this team. Thyroid diseases, including thyroid cancer, have been a
particular area of research.
COMMON QUESTIONS AND HELPFUL                            GLOSSARY         TERMS       FOR

1. If my thyroid gland is removed by surgery, will I need to take thyroid

   Yes, if the whole gland is removed, lifelong thyroid medication is required.

2. How will I know that I am on the right dose of thyroid medication?

   A blood test of the TSH levels will help determine if your dosage of medication is
   right for you. Initially, thyroid medications may need some adjustment to find the right
   dose for each individual. The TSH is usually tested approximately 2 months after
   starting thyroid medication and may be repeated in 2 months until levels are normal.

3. Can enlarged thyroid or goiters get smaller in time?

   The natural history of enlarged thyroid glands is that they continue to enlarge. The
   growth rate will vary. In some persons the gland may enlarge slowly.

4. If the fine needle aspiration (FNA) of the nodule does not show cancer, why is
   surgery recommended?

   Confirming thyroid cancer often requires surgical removal of the nodule and
   surrounding tissues as cancer is defined when the atypical cells extend beyond the
   nodule. The FNA may not obtain a large enough tissue sample to definitely identify
   thyroid cancer.

Nodule of abnormal cell growth; not cancerous.

Endocrine Glands:
A group of organs that secrete hormones.

Normal thyroid function

An enlarged thyroid gland

A cellular protein that travels as a chemical messenger. These chemical messengers
trigger specific cells to do a task.

A syndrome of low thyroid hormones in which one may experience symptoms of lowered
metabolism such weakness and fatigue, usually the TSH levels are elevated, or above

A syndrome of excessive thyroid hormones in which one may experience symptoms of
tremors and insomnia, usually the TSH levels are below normal.

Thyroid Stimulating Hormone; a chemical messenger released from the pituitary gland.
This hormone signals the thyroid gland to produce thyroid hormones. A blood test to
measure TSH is a test of thyroid function.

Thyroid Gland:
An endocrine gland located in the neck which functions to maintain normal body

Surgery to remove the thyroid gland.

An inflammation of the thyroid gland