Introduction. Consensus hasnít been yet achieved about optimal dose quantity that could prevent post therapy hypothyroidism, thus dosing approach varies among different centers. I131 doses can be fixed or calculated, although treatment outcomes donít differ significantly according to recent acknowledgments. Aim. Determination of the incidence of hypothyroidism after radioiodine treatment (I131) in dependence of hyperthyroidism etiology and quantity of applied doses. Materials and methods: The study included 100 patients which have had radioiodine treatment, with a three year post-treatment follow up. The study was conducted at the Nuclear Medicine Department, University Clinical Center of Sarajevo. Data were provided from the patient medical histories. Research is designed as a retrospective, descriptive study. All data were analyzed using Microsoft Excel and the statistical program SPSS 13.0. Results.After the three year follow up, incidence of hypothyroidism within patients with Gravesí disease was 89.5%, with diffuse goiter 50%, with toxic adenoma (TA) 26.8%, and with multinodulare goitre (MNG) 57.1%. Hypothyreoidism in patients with diffuse goiter, Gravesí disease and TA was mostly developed after I131 therapy with a dose quantity of 10.1-15 mCi and in MNG patients after RAI therapy with applied doses of 15.1-20 mCi. Conclusion. The hypothyroidism incidence rate is the highest among patients with Gravesí diseases and the lowest among the TA patients. Itís mostly developed after dose quantity of 10.1-15mCi and it is rare at dose quantity less than 5mCi. 50% of hypothyroidism were developed among patients with diffuse goiter, Gravesídisease.
I131 therapy, hyperthyreoidism treatment, incidence of hypotihyeoidism.