This post will address I-131, Potassium Iodide and the pros and cons of its use during the current Japanese nuclear crisis.
To understand this question, you first must understand the basics of thyroid function.
The thyroid is a gland that secretes hormones responsible for the
metabolism of every cell in your body. This gland utilizes Iodine to
make these hormones. The two main thyroid hormones are called T4 and
T3. The numbers 3 and 4 indicate how many molecules of iodine the
thyroid has attached to create the hormone. T4 is storage hormone - the
body can't use it with 4 molecules of iodine attached, it must convert
it to T3 when needed before the body can use the hormone.
If your thyroid is an engine, Iodine is the fuel.
Potassium Iodide is a form of iodine that the thyroid uses for fuel to make T4 and T3.
The body needs a precise amount of iodine at any given time. Excess
iodine is flushed out of the body when the thyroid and the body are
working properly. Sometimes the thyroid doesn't work properly. If a
person is only taking in an appropriate amount of iodine in each day,
they may not realize they have a thyroid problem.
The thyroid has an 'emergency overload system' that tries to prevent
an accidental overdose of T4 and T3 because you might have eaten too
much iodine. If you consume lots of iodine, the thyroid senses this and
shuts down. It stops using iodine and stops producing thyroid
hormones. This process is not immediate - it takes some time for the
thyroid to sense the extreme overload and shut itself down.
About Radiation risk:
The nuclear radiation in Japan that everyone is talking about right now is in the form of I-131.
In this case, the I stands for Iodine. We are talking about
radioactive iodine - the same substance used in thyroid cancer patients
and Graves' Disease patients to destroy (ablate) their thyroid tissue
Radioactive substances are measured in part by their "half-life".
Their half life is the time of period it takes for half of the radiation
to dissipate. The half life for I-131 is about 8 days. This means if
you are exposed to 30 millirems of I-131, in about 8 days your radiation
levels will be about 15. 8 days later it will be about 7.5. 8 days
later it will be about 3.75 and so on.... Millirems is an older term
that is being replaced in many countries by the term Millisieverts. 10
Millirems = .1 Millisieverts.
To give you an idea of how many MIllisieverts might be dangerous, let me give you some examples:
A chest X-Ray exposes you to about .1 Millisieverts
A CT of the abdomen is about 10 MIllisieverts
The average exposure of evacuees of the Chernobyl disaster was about 31 Millisieverts
The spike noted in Japan was about 400 Millisieverts
Radiation sickness begins at about 1 Sievert (1000 Millisieverts)
This said, there is much evidence that there is increased danger of
cancer to those who undergo x-ray imaging and CT scans. Chernobyl
victims have an increased history of cancer too.
Taking too much potassium iodide with a normal acting thyroid can
cause a condition called Thyrotoxicosis. This means the thyroid pumps
out too much thyroid hormone creating an acute hypERthyroid state that
can be dangerous, or even fatal. In those with thyroid disease - either
diagnosed or undiagnosed - the chances of thyroid storm or thyroid
toxicosis is greatly increased. For some diseases such as Graves'
Disease or for those with "hot" thyroid nodules it is a virtual surety.
Why do we take potassium iodide in a nuclear crisis?
Our thyroids are built to absorb iodine and use it to produce T4 and
T3. Those with poor diets are often slightly deficient in iodine. This
makes our thyroids slightly "hungry" for iodine. When iodine is
absorbed in any form ( the body doesn't care what form you take it) the
thyroid acts like a sponge and tries to absorb it all. When that
happens, it turns it into T4 and T3 and those hormones end up in the
I-131 damages thyroid tissues. Unfortunately it also damages other
tissues in the body as well, but it is especially good at killing the
thyroid. This is why it is used in Graves' and cancer patients.
Potassium Iodide (and any other halide) can block I-131 from
attaching itself to your thyroid. It helps to prevent thyroid damage
from the radioactive iodine because the I-131 will then be excreted out
of the body. It is vitally important that potassium iodide (KI) is
taken only immediately before exposure to I-131. KI will stay in your
system about 24 - 72 hrs after swallowing it. KI may help to protect
your thyroid from the damage of I-131, but it does nothing to protect
the rest of your body from I-131 damage or damage by other types of
Here are some of the possible implications of KI use:
++ becoming hypERthyroid
++ unmasking a dangerous thyroid condition you didn't know you had
++ hypOthyroidism caused when the thyroid shuts itself off
Both hypERthyroidism and hypOthyroidism left untreated can be fatal, so this is quite serious.
There is much controversy about the stockpiling many people are doing
with potassium iodide. Right now experts tell us this is really
unnecessary in the United States, but probably very useful in Japan
where the risk from radioactive I-131 is measurable. Those living
within a certain range of nuclear plants in the United States are
already provided with a supply of potassium iodide for their protection
should a nuclear incident occur. These folks should keep this on hand,
but it is otherwise probably unnecessary for others to do so.
It should be noted that the iodine in table salt is also protective
for your thyroid, but it is unlikely you will be able to consume the
amount of iodine through that route without doing other damage to your
system by way of the salt the iodine is attached to. Consuming too much
salt is dangerous and should be avoided.
If you are deficient in iodine, making sure your body is tested and
being fed the appropriate amount of this trace mineral is helpful for
your health overall, taking into consideration of course that you have
been cleared from autoimmune and other thyroid problems that could
potentially lead to hyperthyroid toxicosis or storm which is very
damaging and could even be fatal.
There is a much greater damage in the United States from bromide and fluoride
(both halides and from the same family as iodine) blocking the body's
use of iodine than a risk of radioactive I-131 hitting our shores from
Japan. If you are concerned about your thyroid and your health from a
very realistic standpoint, testing for fluoride and bromide levels
should be a part of the testing you do to find your iodine and thyroid
status before considering the supplementation of potassium iodide or
other form of iodine for any reason.
I have written frequently about autoimmune thyroid disease here at
WEGO Health and a quick search through the archives will reveal many
other articles as well. Autoimmunity of the thyroid is highly
under-diagnosed as is iodine deficiency, so finding a doctor who
specializes in thyroid care is tantamount to receiving not only a proper
diagnosis but also appropriate treatment for this important condition.
JordanB on March 28, 2011 at 2:41pm