Mortality in patients treated for hyperthyroidism with iodine-131

Area of Science:

• Endocrinology
• Public Health
• Radiology

Background:

• Hyperthyroidism is a significant health concern.
• Radioactive iodine (131I) therapy is a common treatment for hyperthyroidism.
• Long-term mortality risks associated with 131I treatment require further investigation.

Purpose of the Study:

• To investigate the long-term causes of death in Swedish patients treated with 131I for hyperthyroidism.
• To determine if hyperthyroidism or 131I treatment contributes more to mortality.
• To identify specific causes of death and risk factors associated with elevated mortality.

Main Methods:

• A cohort of 10,552 Swedish hyperthyroid patients diagnosed between 1950-1975 and treated with 131I was studied.
• Patient data was linked to the Swedish Cause of Death Register for follow-up.
• Standardized mortality ratios (SMRs) were calculated and compared to the general population, with analyses stratified by sex, follow-up time, and treatment factors.

Main Results:

• Overall standardized mortality ratio (SMR) was 1.47, with higher rates in females (1.50) than males (1.31).
• Cardiovascular diseases were the leading cause of death (61%), with an SMR of 1.65.
• Elevated risks were observed for tumors, endocrine, respiratory, gastro-intestinal diseases, and congenital malformations. Mortality risks decreased over time, except for tumors and trauma. Higher 131I doses and younger age at treatment correlated with higher SMRs.

Conclusions:

• Hyperthyroidism, rather than 131I treatment, appears to be the primary driver of increased mortality.
• Long-term follow-up reveals persistent elevated risks for cardiovascular diseases and tumors.
• Risk stratification by age and 131I dosage highlights specific patient groups with higher mortality.