A GUIDE FOR PHYSICIANS: THYROID EVALUATION OF PATIENTS WHO ARE CONCERNED
ABOUT HANFORD IODINE-131 RELEASES

From 1945 through 1951, radioactive I-131 was released into the
atmosphere from the Hanford Nuclear Reservation during the production of
plutonium for atomic weapons. I-131 releases continued until at least
1957, although at much lower levels than before 1951. Many people
residing in areas near the facility, especially those downwind, have
been concerned about possible adverse health effects from this potential
radiation exposure. Because iodine concentrates normally in the thyroid
gland, the body organ at greatest risk for health effects from I-131
exposure is the thyroid. Although studies to date have not shown a
demonstrable increase in thyroid disease in persons downwind from
Hanford, many individuals remain concerned and wish to be evaluated for
possible thyroid injury. What follows is information and advice to
assist physicians in educating and evaluating patients who desire such
screening.

General points to keep in mind when evaluating these patients:

\* Thyroid disease is relatively common. Therefore, careful screening of
any population will detect individuals with thyroid disease.

\* A finding of thyroid disease in a person who has been potentially
exposed to radiation does not necessarily mean that the disease is
radiation induced.

\* There is no specific test or marker to determine if a thyroid disease
is the result of radiation exposure rather than of other non-radiation
causes.

\* Thyroid evaluation is similar for persons with or without a history
of radiation exposure and does not require special radiation expertise.

Basic screening consists of three elements:

1\) assessing potential risk for radiation exposure,

2\) palpating the thyroid gland,

3\) administering a Thyroid Stimulating Hormone (TSH) blood test.
Patients requesting evaluation should be screened with these three
elements.

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ASSESSING POTENTIAL RISK OF THYROID RADIATION FROM HANFORD I-131
RELEASES

Because I-131 has a half-life of only 8 days, the risk for I-131
radiation injury to the thyroid is limited to a relatively brief time
period immediately after each release occurred. These releases were
greatest in 1945, with lesser releases occurring until 1951. With
knowledge of the prevailing wind patterns at the time of releases, as
well as certain age, residence and milk consumption factors, the Hanford
Environmental Dose Reconstruction (HEDR) study has generated thyroid
dose estimates for the downwind region of Washington State. No method
can determine retrospectively a specific person's exact thyroid
radiation dose, but you can quickly screen patients for Hanford exposure
risk by using the following map and Table 1 to determine if they might
have received thyroid radiation exposure.

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EVALUATION OF THYROID GLAND STRUCTURE AND FUNCTION

PALPATION OF THYROID: Look for enlargement, nodule(s), increased
firmness, fixation to adjacent tissue, adjacent cervical adenopathy.

TSH: Each lab varies slightly in their results, but most give reference
normal range of about 0.4 -- 4.0 mU/L.

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BASIC THYROID WORKUPS

#1 Hypo/hyper workup:

a\. Elevated TSH (probable hypothyroidism): FT4, thyroid peroxidase
antibody (optional).

b\. Low TSH (probable hyperthyroidism): FT4, FT3, I-123 uptake and scan
(to help identify type of hyperthyroidism).

#2 Nodule/goiter work-up:

May include ultrasound, fine needle aspiration (FNA) biopsy of
nodule(s), and thyroid peroxidase antibody.

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SCREENING OUTCOMES (refer to Table 2)

CATEGORY 1:

After thyroid palpation and TSH testing, most patients will fall into
category 1. For patients in this category who have a negative exposure
history, reassurance is sufficient. No further workup is necessary.
However, for those in this category who have a positive exposure
history, or if the patient is strongly concerned, a thyroid ultrasound
is appropriate.

CATEGORY 2:

Abnormal thyroid function resulting in an abnormal TSH but without
palpable changes in the thyroid gland may occur. Both hypothyroidism
(elevated TSH) and hyperthyroidism (low TSH) are relatively common.
Proceed with standard workup and treatment as for any patient, but with
the following modification. Thyroid dysfunction has been correlated with
thyroid irradiation in other studies (but not the Hanford Thyroid
Disease Study). Therefore, if patients in this category who have
elevated TSH also have a positive exposure history, an ultrasound is
recommended to screen for nonpalpable nodules.

CATEGORY 3:

Thyroid enlargement or nodularity with a normal TSH is a common
combination. Proceed with standard workup. If a discrete solitary nodule
is palpable and confirmed by ultrasound, an FNA biopsy is indicated
regardless of nodule size.

When thyroid ultrasound is performed, the following are possible
outcomes:

a\. Normal: What appears to be a nodule by palpation may in fact be a
prominent normal-variant thyroid lobulation. No cancer risk; FNA not
indicated.

b\. Coarse texture: A common finding in hypothyroidism and/or chronic
thyroiditis. No increase in cancer risk indicated.

c\. Small nodule(s) or cysts: Usually not palpable. These are a common
ultrasound finding even in persons with no thyroid disease. (For
example, there is an almost 50% chance of finding one or more such
features in any 60-year-old woman.) They are more common among females,
older adults, and people who have hypothyroidism and chronic
thyroiditis. FNA of nonpalpable ultrasound nodules is indicated when
they are greater than 10 mm average dimension. FNA of even smaller
nodules (less than 10mm) may be indicated with positive radiation
history.

d\. Suspicious nodules: Solitary hypoechoic or complex nodules are more
worrisome for carcinoma than are hyperechoic nodules or multinodular
glands. Nodules with irregular margins or stippled internal
calcifications also are more worrisome. Suspicious nodules warrant FNA.

CATEGORY 4:

These patients have evidence for both structural and functional
abnormalities of the thyroid gland. Proceed with standard workup. Note
comments under categories 2 & 3 above.

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TREATMENT AND/OR REFERRAL OF THE PATIENT

Proceed with treatment or refer as you would any thyroid patient. Use
your usual referral pathway to a thyroid or endocrine specialist.
Special radiation training or expertise is not required.

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TABLE 1. EXPOSURE RISK FROM RESIDENTIAL HISTORY

Hanford Residence History:

-\> Patient born after 1951\*

Exposure Risk From Hanford 1-131 Releases:

-\> No exposure risk, regardless of residence location.

\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

Hanford Residence History:

-\> Patient born prior to 1951 but never resided in a general exposure
area.

Exposure Risk From Hanford 1-131 Releases:

-\> No exposure risk.

\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

Hanford Residence History:

-\> Patient resided in a general exposure area at anytime during
1945-1951

a\. Was age 0-4 yrs during residence\*

b\. Backyard cow or goat as milk source

c\. Resided in central exposure area

Exposure Risk From Hanford 1-131 Releases:

-\> Possible risk of thyroid radiation (a, b, and c increases exposure
above)

\*Children older than 4 years at exposure are also at increased risk,
though not as high as below age 4; adults older than 40 years at
exposure are at greatly reduced risk.

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TABLE 2. Thyroid Evaluation Guidelines

\_\_\_\_\_\_\_\_\_\_\_

CATEGORY 1

TYROID PALPATION = Normal

TSH = Normal

BASIC THYROID WORK-UP = None

COMMENTS = Reassure if no exposure. Perform ultrasound if positive
exposure history exists.

\_\_\_\_\_\_\_\_\_\_\_

CATEGORY 2

TYROID PALPATION = Normal

TSH = Abnormal

BASIC THYROID WORK-UP = Yes, see #1 above

COMMENTS = Perform ultrasound if positive exposure history exists.

\_\_\_\_\_\_\_\_\_\_\_

CATEGORY 3

TYROID PALPATION = Abnormal

TSH = Normal

BASIC THYROID WORK-UP = Yes, see #2 above

COMMENTS = Perform ultrasound if positive exposure history exists. Add
FNA\'s of nodule(s) greater than 10mm

\_\_\_\_\_\_\_\_\_\_\_

CATEGORY 4

TYROID PALPATION = Abnormal

TSH = Abnormal

BASIC THYROID WORK-UP = Yes, see #1 & #2 above

COMMENTS = Perform ultrasound if positive exposure history exists. Add
FNA\'s of nodule(s) greater than 10mm

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REFERENCES

Hanford Environmental Dose Reconstruction Project, CDC, April 1994

Radiation Exposure from Iodine 131, ATSDR Case Studies in Environmental
Medicine, ATSDR, November 2002
(http://www.atsdr.cdc.gov/HEC/CSEM/iodine)

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ADDITIONAL RESOURCES

Hanford Thyroid Disease Study Final Report:

http://www.cdc.gov/nceh/radiation/hanford/htdsweb/

Hanford Community Health Project:

www.hanfordhealth.info

American College of Preventive Medicine 1-131 Webpage:

www.iodinel31.org

National Cancer Institute:

www.cancer.gov/il31

Centers for Disease Control and Prevention:

www.cdc.gov/nceh/radiation

American Thyroid Association:

www.thyroid.org

American Association of Clinical Endocrinology:

www.aace.com

This guide was developed by the Hanford Community Health Project, which
is sponsored by the Agency for Toxic Substances and Disease Registry
(ATSDR), in collaboration with the American College of Preventive
Medicine.

The content of the guide has been reviewed and endorsed by the following
organizations:

AMERICAN THYROID ASSOCIATION

AMERICAN ASSOCIATION OF CLINICAL ENDOCRINOLOGISTS

AMERICAN COLLEGE OF PREVENTIVE MEDICINE

December 2004