WHAT IS THE THYROID?
The thyroid is a small gland which appears very much like a
butterfly, or a bat, in its shape. It is located in front of the windpipe just below the
Adam's apple, just beneath the skin of the neck. The thyroid weighs less than an ounce,
but it can have an enormous impact on your health.
Think of the thyroid as the body's regulator. It does its
job by releasing 2 thyroid hormones, T3 and T4, that affect most organs of the body
including the heart, brain, liver, kidneys, skin..., even the growth of your hair. These
hormones help regulate the heartbeat, body temperature, how quickly a person burns
calories, how swiftly food moves through the digestive tract, and more.
Normally, the thyroid doles out just the right amount of
thyroid hormone to keep these processes humming smoothly. But, it may become overactive
and pump out too much hormone, or underactive and pump out too little. Either way, the
abnormal thyroid hormone levels can profoundly effect the body's metabolism.
WHAT IS A THYROID NODULE?
When the thyroid is enlarged, the medical term is a goiter.
If the thyroid has one large area and the rest of the thyroid is normal in size, this is
called a thyroid nodule. Should there be many thyroid nodules, the thyroid is then called
a multi-nodular goiter.
A simple goiter can be due to many different illnesses and
truly depends on what the underlying difficulty is. A multi-nodular goiter is also
possible from a large number of causes, the most common of which is Hashimoto's
thyroiditis with or without hypothyroidism. (For a greater explanation of hypothyroidism
and Hashimoto's thyroiditis, please see our pamphlet entitled, Hypothyroidism.)
Single thyroid nodules can also be due to a number of
different reasons. By far, thyroid nodules are made up of thyroid cells which have tended
to grow out of proportion to the rest of the thyroid gland around it. In almost all
circumstances or 90% of the time, these cells are completely benign and do not represent
any form of cancer or tumor.
WHAT ARE SOME DANGER SIGNS?
There are some circumstances, however, which may indicate a
slightly greater chance of a single thyroid nodule representing a tumor rather than being
benign. These might include rapid growth, tenderness over the area, hoarseness or loss of
weight.
In the past, one of the predisposing reasons for the
development of tumors of the thyroid was that some people, when they were younger, were
exposed to radiation therapy to the head or neck area for treatment of many childhood
illnesses including croup, whooping cough, tonsillitis and mumps. As soon as this practice
was found to be detrimental, it was abandoned.
However, all individuals who were exposed to radiation
therapy to the head and neck area as a child during those times should have any suspicious
thyroid nodule evaluated thoroughly. Because there are many more reasons to have a
completely benign thyroid nodule than there is to have one that contains a tumor, these
causes are always searched for when evaluating a thyroid nodule including over or under
activity of the thyroid gland or Hashimoto's thyroiditis.
WHAT TYPE OF TESTING IS AVAILABLE?
In the absence of any of the above problems being found,
after blood testing requested usually by your endocrinologist, he or she may suggest the
use of other techniques to evaluate what the nodule is made of.
One technique involves doing a thyroid scan. This involves
taking a capsule by mouth of a very small dose of radioactive iodine which is absorbed and
travels to the thyroid and makes it able to have a picture taken of it. What this picture
looks like sometimes gives us an idea of what the nodule is made of.
It is a very safe test but should generally not be
administered to women who are pregnant or who are considering becoming pregnant in the
very near future. There is no danger of any damage from the radioactive iodine to the
person himself or herself. There is only a theoretical potential of problems to an unborn
child and therefore we try not to scan patients who are pregnant or who will be pregnant
soon.
Another examination that might be performed is an
ultrasound of the thyroid. In the same way that submarine or airplane radar sends sound
waves out which bounce off from other objects and come back to register on a screen to
tell the pilot what is out there, a thyroid sonogram involves the placement of a
microphone on the neck which sends sound waves down into the neck which bounce back to the
microphone and tell the microphone what the thyroid looks like. It involves no needles, no
radiation, no pain and is sometimes even felt as a relaxing massage of the neck!
The previous two examination methods give valuable
information regarding the structure of the thyroid. However, in everyday usage, it has
been found that the single best examination to gain the most possible information
regarding what a thyroid nodule contains within it, is a fine needle aspiration biopsy of
the thyroid.
WHAT IS A "FINE NEEDLE ASPIRATION BIOPSY" OF A
THYROID NODULE?
This is performed by taking a small needle and injecting
"Novocaine" into the skin of the neck. This is so you will not feel the needle
going into the neck. At that time, while the skin is numb, a needle (which is smaller than
the needle used to take blood from your arm) is passed through the skin into the thyroid
nodule. Some cells are sucked up into the needle and then placed on slides to be sent to a
pathologist for review.
The procedure is performed in the doctor's office, does not
require hospitalization, does not require general anesthesia, and the patient is ready to
walk out of the office as soon as the procedure is finished. There is very little
discomfort involved, and most patients say that the slight stinging sensation that they
get when the local anesthetic is injected into the skin is the worst part of the whole
procedure!
WHAT IS THYROID HORMONE SUPPRESSION THERAPY?
Depending upon the results of the biopsy, surgery may be
indicated or a use of thyroid hormone known as thyroid hormone suppression therapy may be
indicated. Thyroid hormone suppression therapy works on the same principle as placing a
heater in a room with a thermostat. If you can imagine a heater which warms a room warm
enough to turn the thermostat in that room off, and thereby turn the main furnace in the
basement off, that is how thyroid hormone suppression therapy works.
By somebody taking thyroid hormone, enough to turn the
"thyroid thermostat" off, there is no further stimulation of the thyroid nodule
to grow. Therefore, one would expect that when using thyroid hormone suppression therapy,
the thyroid hormone will cause the nodule to not grow (which is what is seen most of the
time) or even to shrink somewhat in size (seen somewhat but less frequently).
Thyroid hormone suppression therapy therefore is a valuable
aid in preventing the further growth of the thyroid nodule. Not only that, should the
thyroid nodule continue to grow while on thyroid hormone suppression therapy judged as
adequate by your endocrinologist, it also serves as a discriminatory test which suggests
that the thyroid nodule is aggressive in nature, and should probably be removed
surgically.
The above is a broad summary of some of the important
considerations in evaluating and treating a thyroid nodule. There are many other
considerations that need to be taken into account as well as many questions that you might
have concerning the above. Please don't hesitate to discuss them with your physician as
they are extremely important.
This pamphlet was prepared exclusively by Michael David Hein,
M.D., an Endocrinologist in private practice in Providence, Rhode Island, as a service to
his patients and to interested parties, in accordance with currently available scientific
data and accepted Endocrinologic practice. It is not, nor is it meant to be, a substitute
for actual medical care, and its advice and directives are meant
to supercede those of your private physician. Dr. Hein is responsible for this articles
content, and would be happy to answer any questions you might have after reading it.