Thyroid uptake of 123I in a normal population

Area of Science:

• Nuclear medicine
• Endocrinology
• Radiology

Background:

• Iodine 131 (131I) poses carcinogenic radiation risks to the thyroid during uptake and scan procedures.
• Iodine 123 (123I) provides comparable uptake study results to 131I but with substantially lower thyroid radiation exposure.
• Observed fluctuations in thyroidal iodine uptake and potential 131I radiation injury necessitate re-evaluation of normal uptake values.

Purpose of the Study:

• To determine the normal range of thyroidal iodine uptake using 123I in a euthyroid population.
• To assess the clinical reliability and safety of 123I for thyroid uptake studies.
• To compare current 123I uptake values with historical data.

Main Methods:

• A study involving 100 euthyroid subjects was conducted.
• Thyroidal iodine uptake was measured using purified 123I at two and 24 hours.
• Uptake values were analyzed in relation to various physiological and demographic factors.

Main Results:

• The established normal range for 123I uptake was 1%–8.8% at two hours and 4%–27% at 24 hours.
• These values are significantly lower than those reported eight years prior.
• No correlation was found between uptake values and thyroid indices, age, sex, ponderal index, estrogen use, or urinary iodine excretion.

Conclusions:

• Purified 123I is a clinically reliable agent for thyroid uptake studies.
• Utilizing 123I significantly reduces the potential for radiation injury compared to 131I.
• Current normal thyroidal iodine uptake ranges appear to be lower than previously established.