Endocrine Abstracts

Introduction: Radioiodine (RAI) is used as a definitive therapy of hyperthyroidism due to toxic adenoma (TA) as well as toxic multinodular goiter (TMG). Achievement of hypothyroidism or euthyroidism is defined as a successful therapy.

Methods: The study was conducted in 666 patients – 484 with TA and 182 with TMG (85.58% of women), aged 56.19±13.88 years. We analyzed retrospectively hormonal and imaging findings (scintigraphy, ultrasonography), including isotopic results in subjects treated at Department of Nuclear Medicine and Endocrinology Department during the eight-year period. The efficacy of RAI therapy has been assessed based on free thyroid hormones levels, measured 12 months after radioiodine administration.

Results: Mean concentrations of FT4 and FT3 and age did not differ significantly both groups. Patients with TA had lower thyroid mass and RAI 24-h uptake than subjects with TMG (P=0.0000). Administered therapeutic activities of RAI (MBq), calculated using Marinelli’s formula, were smaller in subjects with TA (537.03±181.39 vs 614.13±147.22; P=0.0000) and the thyroid-absorbed doses of RAI (Gy) in such patients were greater (P=0.0000). After RAI therapy, hypothyroidism was found in 3.30% TA and 8.79% TMG participants, euthyreosis - in 80.79% TA and 69.23% TMG and hyperthyroidism – in 15.91% TA and 21.98% TMG. The efficacy of RAI therapy was achieved in 84.10% of TA patients (F–84.99%; M-78.87%) and in 78.02% of TMG subjects (F–75.80%; M-92.00%). The cure of hyperthyroidism was significantly correlated in both groups with lower: thyroid mass, RAI 24-h uptake and concentrations of FT4 and FT3 before therapy. No significant associations between successful therapy and patients’ age, thyroid absorbed dose and used therapeutic activity of RAI were found.

Conclusions: RAI therapy was more effective in TA patients. Males responded better to treatment than females in case of TMG. The cure correlated with thyroid mass, RAI 24-h uptake and free thyroid hormones levels before therapy.