Endocrine Abstracts

Two female patients aged 44 (PtA) and 68 years old (PtB) with non-toxic nodular goitre for more than 10 years were treated with radioiodine therapy. High resolution ultrasonography show enlarged thyroid glands 50 ml, with two nodules in left and right lobe in PtA and 58 ml with one nodule in the left lobe in PtB. Serum TSH, fT₄ and fT₃ were in normal ranges. Malignancy was ruled out by ultrasound-guided fine-needle aspiration biopsy. In PtA thyroid radioiodine scintigraphy showed homogenous and diffuse uptake, with 33% radioiodine uptake (RAIU) after 24 h; and homogenous uptake, with 32% RAIU in PtB. The effective half-life was 7 days for both patients. The activity dose was calculated by Marinelli’s formula and PtA received 280 MBq and PtB receive 600 MBq of I-131. Follow-up control was done every 4 weeks. Hyperthyroidism was induced after 3 months of radioiodine therapy in PtA and after 5 months in PtB. TSH serum levels decreased and serum FT₄ and FT₃ increased. The levels of TSH receptor antibodies were positive in both patients, the anti thyroglobulin and anti peroxidase antibodies were within normal range. thyroid scintigraphy showed homogenous and diffuse uptake in both lobes with small reduction in the thyroid volume. RAIU after 24 h was 53% for PtA and 48% for PtB. Both patients received antithyroid drugs to control the hyperthyroidism. After 6 months of radioiodine therapy both patients received second dose of radioiodine therapy 400 MBq each. After 3 months of the therapy PtA developed hypothyroidism and PtB was in euthyroid state. Radioiodine therapy is non-invasive, safe and cost effective method of therapy for reduction of goitre even in patient with low radioiodine uptake. In these cases radioiodine therapy induce hyperthyroidism, this may be due to the activation of silent Graves’ disease in these patients.