Changing normal values for thyroid uptake of radioactive iodine

Area of Science:

• Nuclear Medicine
• Endocrinology
• Thyroidology

Background:

• The 24-hour radioactive iodine uptake (RAIU) is a key diagnostic test for thyroid gland function.
• Traditional RAIU normal ranges (15%-45%) are outdated due to evolving dietary iodine levels.
• Recent revised ranges (9%-32%) are also questioned in areas with fluctuating iodine intake.

Purpose of the Study:

• To determine current normal 24-hour radioactive iodine uptake values in a population with stable dietary iodine intake.
• To compare these values with historical and recently revised ranges.
• To emphasize the need for localized normal range establishment in nuclear medicine.

Main Methods:

• Analysis of 24-hour radioactive iodine uptake data from a defined population in Ft. Smith, Arkansas.
• Focus on a cohort without significant exposure to high-iodine content bread.
• Comparison of uptake values between men and women.

Main Results:

• The study confirmed a national trend of decreasing RAIU values, suggesting a normal range of 11% to 30%.
• Specific ranges were identified: 11% to 23% for men and 13% to 32% for women.
• These findings indicate a shift from older, higher normal ranges.

Conclusions:

• Current 24-hour radioactive iodine uptake values are significantly lower than traditional ranges.
• Nuclear medicine departments must establish and regularly re-evaluate their own normal RAIU ranges.
• Dietary iodine content is a critical factor influencing normal RAIU values and necessitates ongoing monitoring.