Endocrine Abstracts

Aim: Radioactive iodine (RAI) ablation therapy is used as part of the treatment for hyperthyroidism. Recently, low dose applied ¹³¹I treatment for hyperthyroidism has decreased the need for thyroidectomy. The aim of this study was to evaluate serum fasting glucose (FG) values in pre and post treatment RAI patients.

Materials and Methods: Thirty-two patients with hyperthyroidism (mean age 56.0±14.5 years; range 24–83) treated with a single therapeutic dose of ¹³¹I (range 8–15 μCi) in our endocrinology department between 2009 and 2013 years were included this study. Before ¹³¹I administration, one patient had subclinical hyperthyroidism and 31 patients had overt hyperthyroidism. Post treatment follow-up ranged from 1 to 4 years for long-term effect of RAI treatment. Clinical and biochemical assessment with FG, lipid profile, free T_3, free T₄ and TSH were performed approximately every 3 months during the first year and at longer intervals afterwards. All these parameters were reevaluated at least after 1 year post treatment.

Results: Before RAI treatment mean free T₃ levels was 4.6±1.5 pg/ml; mean free T₄ levels was 1.5±0.7 ng/dl; TSH levels was 0.1±0.2 μIU/ml; FG levels was 95.1±20.2 mg/dl; LDL-cholesterol levels was 108.6±39.5 mg/dl. After RAI treatment the free T₃ levels was 3.07±0.5 pg/ml; free T₄ levels was 1.1±0.2 ng/dl; TSH levels was 1.6±1.3 μIU/ml: FG levels was 121.5±48.2 mg/dl; and LDL-cholesterol levels was 122.6±31.7 mg/dl. Serum fasting glucose and LDL-cholesterol levels after the RAI treatment were significantly different from pretreatment levels (P=0.002 and P=0.043 respectively).

Conclusions: We demonstrated that glucose metabolism in the patients with hyperthyroidism might be impaired after RAI ablation treatment despite exposure to limiting dose of the radiation. We suggest that serum fasting glucose levels must be more carefully follow-up after RAI ablation treatment. There is a need for further prospective study which was clarified relationship between serum fasting glucose and RAI therapy.