Endocrine Abstracts

Background: In Belgium, a land with borderline iodine intake, the prevalence of goiter is 6 to 40%. This raises the question of an economically affordable treatment with few side effects. In euthyroid goiters, the effect of radioiodine on volume reduction is debated. Most data were described last century and do not take into account recent thyroid hormone measurements, newer ultrasonography techniques and changes in iodine supplementation. Doses administered in the past and elsewhere in Europe exceed doses used in Belgium on ambulatory basis.

Patients and methods: Between 2010 and 2017, 211 patients with a euthyroid or a subclinical hyperthyroid multinodular goiter were treated with ¹³¹I. Patients had a baseline echography and thyroid function tests. After one, three, six and twelve months, a blood test was carried out. Control ultrasound was scheduled after six and twelve months.

Results: The median volume reduction was 24% after six and 42% after twelve months. An overall tendency indicates a decreasing fT4 and an increase in TSH after a one year follow-up. 24 patients developed transient hyperthyroidism one to three months after treatment and 11 received antithyroid agents. Two patients had emergence of TSI one month after treatment. Definite hypothyroidism developed in 13 patients, necessitating substitution. Both dose of radioiodine and the baseline volume have a significant influence on volume reduction six months post-treatment. Baseline volume also influences volume reduction after twelve months.

Conclusion: A significant decrease in thyroid volume was observed six and twelve months after treatment with radioactive iodine for a non-toxic multinodular goiter.