Finding It and Treating It Using Radioiodine
Your doctor has referred you to Nuclear
Medicine to learn more about the extent of
your thyroid cancer, and perhaps even for
treatment of the cancer. Please feel free to
direct any questions or concerns you might
have either to your doctor or to one of our
Nuclear Medicine doctors.
What Does the Thyroid Do?
The thyroid is a small, butterfly-shaped
gland that sits below the Adam’s apple. It
helps to control your body’s metabolism. It
works to produce thyroid hormones, which
travel throughout the body. When the
thyroid is working as it should, it also takes
up iodine. Thyroid cancer cells which take
up iodine are “well differentiated.” This
means that these cancer cells have not
changed much. If they are well
differentiated, they are still working in many
ways as you might expect normal thyroid
gland cells to work.
What Kinds of Thyroid Cancer Are
The two most common forms of thyroid
cancer which can be treated are papillary
and follicular. These are the types that often
take up radioiodine just like normal thyroid
What Is the Treatment for Thyroid
Thyroid cancer treatment can be thought of
as a process. The process includes:
ξ Surgery to remove the thyroid gland.
ξ Thyroid ablation to rid the body of
“left over” thyroid cells with use of a
ξ Blood tests to check TSH and
ξ Total body radioiodine metastatic
survey scans to check for remnants
of the thyroid as well as for any
spread of cancer cells. There are
special instructions listed below.
The scans may be done more than
one time in order to follow progress
ξ Hormone replacement to replace the
hormone once made by the thyroid
The first line of treatment for most thyroid
cancer is surgery. About 4 weeks later, a
dose of radioactive iodine is used to destroy
any thyroid tissue that may have been left
after the surgery. After the thyroid gland is
destroyed, patients need pills to replace the
thyroid hormone that would have been made
by the thyroid gland.
What Is Thyroid Ablation?
This is done in the Nuclear Medicine. It is
often used to remove (ablate) any thyroid
tissue that may remain behind in your neck
after surgery. This is done by giving you
some radioactive iodine that will destroy the
small amount of thyroid tissue left in your
neck after surgery. You do not need to
remain in the hospital after this treatment.
Most of the time this is done a month after
surgery and a capsule of radioactive iodine is
given when the TSH test is high (greater
than 40 units). Sometimes your endocrine
physician uses Thyrogen ®, a synthetic
thyroid stimulating hormone.
How Does Radioactive Iodine Work?
Iodine is taken up by the normal thyroid
gland and most (~ 70%) thyroid cancers.
When the cells take up iodine, they also take
up radioiodine or iodine-131, which is a
radioactive form of iodine. Iodine that is
radioactive can be used to find and treat
thyroid cancer. It is one of the oldest and
best forms of cancer treatment for any
thyroid cancer that will take up radioiodine.
It destroys cancer cells.
What Is a Metastatic Survey?
This survey scan is also done in Nuclear
Medicine for patients with thyroid cancer.
Most often it is done after thyroid surgery
and ablation, and again at other future times
as needed. It is used to find out if there is
any spread of cancer (metastases) to other
parts of your body.
For the survey, you will be given a capsule
of radioactive iodine to swallow. It will
travel to any thyroid tissue and to most
thyroid metastases. You will return to
Nuclear Medicine after 2-7 days later, and
images of your body will be made. These
will show how much thyroid tissue is left in
your neck and whether or not there is any
spread of the cancer.
How do I Prepare for a Metastatic
If you have been taking any thyroid hormone
pills, you might be asked to stop them about
a month before the survey, since they will
impact the test. If you stopped your thyroid
replacement pills, you will be told when you
should start taking these pills again after
taking the radioiodine and scan. Sometimes
another method is used where we inject
synthetic human thyroid stimulating
hormone (Thyrogen ®) so you would not
need to stop thyroid hormone therapy.
Thyrogen ® has also been approved for
thyroid remnant ablation, and may be used
in treatment of thyroid metastases. There is
a special schedule of injections, dosing with
radioiodine, blood tests, and thyroid
When the survey is scheduled, you will also
be scheduled to have a TSH blood test done
about two days before the survey. A sample
may also be taken to measure serum
You may be asked to maintain a low iodine
diet for about ten days in order to allow the
test to work better. To do this, you should
avoid milk & dairy products, seafood, kelp,
bread, cereal and many seasonings (above all
salt which has had iodine added). Most
fruits, vegetables and meats that have not
been processed are fine.
Please tell us if you have had an x-ray using
contrast in the last few weeks. You must not
be pregnant or breast feeding when you
receive radioiodine. You should not plan to
become pregnant in the next 6 months. You
should not father a child for 6 months.
How Is Metastatic Thyroid Cancer
If your survey shows spread of thyroid
cancer to other parts of your body, your
doctor may discuss treatment with a larger
amount of radioactive iodine than that used
for simple thyroid ablation.
How Should I Take Care of Myself after I
Most of the radioiodine that is not taken up
by thyroid tissue will leave your body within
about two days. Most is lost through your
urine, but some is also released in saliva,
sweat, and stool. In order to help remove
the extra radioactivity, you should drink
extra fluids and empty your bladder often
(about every 1-2 hours or so) for the first 2
days. During the first two days after the
dose, drink plenty of juices and water. You
should try to have at least one bowel
movement each day. Add fiber and prune
juice to your diet if needed. You may need a
laxative if you are having trouble with bowel
movements. You might be advised to take
lemon candies to increase saliva secretion
after you take the radioiodine capsule.
Radiation Safety Measures for You
The dose of radioiodine used to perform a
metastatic survey is most often small. Doses
used in thyroid ablations are greater, with
the largest doses used for treatment of
thyroid cancer metastases. People around
you are at very low risk from the radiation.
There are things that you can do in the first
two to three days to lessen the risk for
Do not return to work until the next
Limit your time in public places.
Do not travel by airplane or
prolonged car trips for two days.
Maintain an arm's length distance
from other people if you will be with
them for long stretches of time.and
double this distance for pregnant
women and children (2 arms
lengths). The amount of radiation
exposure will decrease quickly as the
distance is increased. Maintain this
for four (4) days.
Flush the toilet twice after using it.
Brush once under the rim of the toilet
with the toilet brush and re-flush. If
you can, use a toilet that others won’t
Avoid sharing of eating utensils.
After use, you can wash your utensils
Use fluids and lemon candies, as
Sleep alone in bed for four (4) days.
Avoid close contact with children
and pregnant women.
If you think you are pregnant, inform
your doctor because radioiodine
should not be given to pregnant
women. After you receive
radioiodine, you should avoid getting
pregnant for about six months.
Radioiodine will show up in breast
milk. Inform your doctor if you are
You should not try to get pregnant or
father a child for at least six months
after treatment with radioiodine.
Frequently Asked Radiation Questions
Can I continue breast feeding?
Absolutely not! The radioiodine absorbed
by a breast feeding infant can lead to
permanent thyroid gland problems. External
radiation exposure to the baby will result
from being close to the mother’s breast (the
radioiodine will accumulate in the breast of
a breast-feeding mother) and being close to
the mother’s radioactive thyroid gland.
Therefore, breast feeding must be stopped
well before the mother’s radioiodine
treatment. Nursing may resume after the
birth of your next child.
I am still lactating. Is that a problem?
Yes, a big one! The radiation dose to the
lactating breast can be large. Lactation must
be fully ended well before treatment. If you
abstain from nursing for 2-3 months prior to
treatment, we can be sure that lactation (and
the ability of the breast to concentrate large
amounts of iodine) doesn’t increase your
I have children at home? What should I
Plan to limit contact with them for at least
four (4) days. Always keep in mind the
“arm’s length rule.” To resist the temptation
of children coming close to you during this
time, it is best to make plans for the children
to spend most of this time with other family
I am planning on staying at a hotel for a
few days just to play it safe. What do you
We strongly advise you not to do this.
Although reassuring to your loved ones, this
will expose the public (housekeeping staff
and other patrons) to radiation. We know
that the toilet you use will be a source of
radiation exposure since most of the
radioiodine is passed through the urine.
This is why we advise you to use your own
bathroom for a few days and avoid using
How long should I wait to get pregnant
after having radioiodine treatment?
We advise you to wait at least 6 months.
Do I need any tests prior to treatment?
Hospital policy mandates a pregnancy test
on the day before or the day of treatment for
all women of childbearing age.
I don’t need a pregnancy test because my
husband had a vasectomy, right?
Wrong! Please refer to the answer above.
How do all these radiation safety
measures apply to pets?
Treat them as people or, better yet, children.
Their thyroid glands are much more
sensitive than adult human thyroid glands,
so besides the “double-arm’s length rule,”
we also advise you to limit holding your pets
for four (4) days.
Any Further Questions?
If you are a UW Health Patient and have any
other questions or concerns, we will gladly
help you with them. You can reach us at
(608) 263-1462. If you are a UW Health
Patient and live out of the area, call
1-800-323-8942 and ask for the Nuclear
Your health care team may have given you this
information as part of your care. If so, please use it
and call if you have any questions. If this information
was not given to you as part of your care, please
check with your doctor. This is not medical advice.
This is not to be used for diagnosis or treatment of
any medical condition. Because each person’s health
needs are different, you should talk with your doctor
or others on your health care team when using this
information. If you have an emergency, please call
911. Copyright © 5/2017. University of Wisconsin
Hospitals and Clinics Authority. All rights reserved.
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