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Thyroid nodularity after diagnostic administration of iodine-131
P Hall1, C J Fürst, A Mattsson
1Department of Oncology, Radiumhemmet, Karolinska Hospital, Stockholm, Sweden.
Radiation Research
|December 1, 1996
Summary
Diagnostic radioiodine (131I) exposure in women showed a slight, possibly non-causal, association with thyroid nodules. This study found no evidence of 131I causing thyroid cancer in adults.
Area of Science:
- Nuclear Medicine
- Radiological Health
- Endocrinology
Background:
- Internal radioiodine (131I) risks are less understood than external radiation.
- Diagnostic 131I use is widespread, necessitating risk assessment.
- Concerns exist regarding radioiodine release from nuclear incidents.
Purpose of the Study:
- To investigate the risk of thyroid nodularity in women exposed to diagnostic radioiodine (131I).
- To evaluate the association between 131I dose and thyroid nodule development.
- To compare nodularity rates between exposed and non-exposed women.
Main Methods:
- A cohort study comparing 1,005 women exposed to diagnostic 131I (1952-1977) with 248 non-exposed women.
- Clinical examination including thyroid palpation was performed (1991-1993).
- Odds ratios were calculated to estimate relative risk (RR) for thyroid nodularity.
Main Results:
- Prevalence of thyroid nodularity was similar between exposed (10.6%) and non-exposed (11.7%) groups (RR=0.9).
- A positive association was observed between 131I dose and nodularity (excess RR=0.9 per Gy).
- Age at exposure did not significantly modify the risk, unlike external radiation findings.
Conclusions:
- Diagnostic 131I administration showed a potential association with thyroid nodules, but causality is uncertain due to confounding factors.
- No thyroid cancers were detected, suggesting diagnostic 131I rarely causes thyroid cancer in adults.
- Further research is needed to clarify the causal link between diagnostic 131I and thyroid nodularity.