Enhancing the efficacy of (131)I therapy in non-toxic multinodular goitre with appropriate use of methimazole: an analysis of randomized controlled study

PURPOSE: It is possible to raise the rate of the uptake of (131)I in the thyroid gland (RAIU) by increasing the endogenous TSH level through appropriate use of methimazole (MMI) prior to (131)I therapy. The purpose of this paper is to assess the impact of pre treatment with MMI on the efficacy of (131)I therapy in non-toxic multinodular goitre (NMG). METHODS: Thirty-one patients with NMG received (131)I treatment in order to reduce the volume of the thyroid (TVR). Those in group 1 (n = 16) were administered 10 mg of methimazole for 6 weeks. Four days after its discontinuation, they received (131)I. Patients in group 2 (n = 15) were given a placebo instead of MMI. The therapeutic activity of (131)I was constant (800 MBq) and was repeated every 6 months. Treatment was discontinued when TVR reached <40 ml. RESULTS: In group 1, RAIU increased approximately twofold. Ten patients from group 2 and four patients from group 1 received further doses of (131)I. The median of time until TVR decreased below 40 ml was 9 months [6–12 months] and 18 months [14–22 months] in group 2. At 2 years after the (131)I therapy, the occurrence of hypothyroidism did not differ significantly (36% in group 1 and 33% in group2, p = 0.074). CONCLUSIONS: Radioiodine treatment of NMG preceded with appropriate application of MMI is efficient thanks to increased RAIU, shorter period of treatment, and lower frequency of (131)I administration, without an increase in the incidence of post-treatment hypothyroidism.