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Re: reported side effects from CT scan of head
Rarely (and I do mean rarely), patients who receive iodinated contrast
material for CT can develop iodine-induced hyperthyroidism. This has
nothing whatsoever to do with the radiation exposure form the CT
examination.
The appended reference is an older review article, but it will point you in
the right direction.
Barry A. Siegel, M.D.
siegelb@mir.wustl.edu
Authors
Fradkin JE. Wolff J.
Title
Iodide-induced thyrotoxicosis. [Review] [292 refs]
Source
Medicine. 62(1):1-20, 1983 Jan.
Local Messages
Held by Becker
Abstract
Iodide-induced thyrotoxicosis (IIT) occurs in patients with: 1)
endemic goiter; 2) nonendemic goiter; 3) no previous thyroid disease.
Iodine prophylaxis for endemic goiter caused transient increase of
0.01-0.04% over the basal incidence of hyperthyroidism peaking at 1-3
years and normalizing in 3-10 years despite continued iodide
exposure. Elderly subjects with large nodular goiters of long
standing are at greater risk. In nonendemic areas, iodine-containing
drugs such as amiodarone, radiographic contrast media or
iodochlorhydroxyquinoline are implicated in IIT more often than
iodides. With nonendemic goiter, IIT occurs more commonly in women
whereas, in the absence of preexisting thyroid disease, men are more
often affected. In both groups, exophthalmos and antithyroid
antibodies are absent, radioiodine uptake is low, there is no thyroid
tenderness or pain, and the hyperthyroidism is self-limited (1-6
months) and should thus be treated conservatively. IIT occurs more
frequently in areas of marginal iodine intake (Europe) than in the
U.S. In view of the extensive exposure to iodine, it is a rare
complication in this country. It is postulated that defective
autoregulation of hormone biosynthesis may contribute to IIT.
[References: 292]
Carol Marcus
<csmarcus@ucla.edu> To: JGinniver@AOL.COM, radsafe@list.vanderbilt.edu
Sent by: cc:
owner-radsafe@list.van Subject: Re: reported side effects from CT scan of head
derbilt.edu
11/28/03 04:45 PM
Please respond to
Carol Marcus
At 11:25 AM 11/28/2003, JGinniver@AOL.COM wrote:
A relative recently went to an Ear Nose and Throat Specialist due to
sinus problems. Unfortunately the specialist was unable to identify
the cause. The next step, which the specialist was reluctant to take
was a CT Scan, presumably of the head. The specialist stated that
unless the symptoms became more severe that s/he wouldn't authorise
the CT scan due to the high levels of radiation involved. The
specialist then went on to state that some individuals who had
recived CT scan (again presumably of the head) had experienced
thyroid problems.
I don't wish to debate the merits or not of prescribing the CT
examination. The Doctors decision not to do this is consistent with
guidance in the UK that they shouldn;t not prescribe a radiation
examination unless they believe it is justified and that the benefits
outweigh the risk, albeit small, of the radiation exposure.
What I would like assistance with is the validity of the statement
that a proportion of patients who have recieved CT scans have then
experienced thyroid problems. Based on current evidence I don't
believe that this is possible, but Medical Physics is not my field
and I would be grateful if others with knowledge and experience in
this area could help. Has there every been any published study that
has managed to identify a statistical link between CT scans and
Thyroid problems. I intend to write to the Doctor to establish the
reason for this statement, but would like some more information, if
it's available, before I do so.
Thanks for any help you can all provide.
Regards,
Julian
Dear Julian and Radsafers:
It is absolutely impossible to have thyroid effects from a CT scan of the
head, and I have never heard of a study showing any. This is probably just
an excuse not to order a somewhat expensive test.
Ciao, Carol
Carol S. Marcus, Ph.D., M.D.
<csmarcus@ucla.edu>