Endocrine Abstracts

Introduction: Smoking is an independent risk factor for Graves’ disease (GD) and an independent predictor for Graves’ophtalmopathy (GO), but the influence on hyperthyroidism severity was not established.

Aim: To evaluate the relationship between smoking and thyroid function at diagnosis and after administration of antithyroid drugs (ATDs) in GD patients.

Materials and methods: We prospectively investigated 116 newly diagnosed, untreated GD patients, 82.8% females, mean age 43.8±15.2 years. At diagnosis we recorded: demografic characteristics, smoking status (non-smoker 63.8%, current smoker 36.2%), presence of ophtalmopathy, goiter size, autoantibody titer, serum concentrations of TSH, FT₄, FT₃, TT₃, and usual biochemistry. All patients received treatment with methimazole and were followed (mean 12±9 months) at 2 months with physical exam and FT₄, TT₃, TSH at least until TSH levels returned to normal (>0.4 mUI/ml). We recorded the time needed for the return of thyroid hormones (THRN) and TSH (TTRN) levels to normal.

Results: There was no difference in current smoking percentage between females (33.3%) and males (50%), P=0.15. Smoker males presented lower FT₃ (P<0.001), higher FT₄/FT₃ (P<0.001) at diagnosis and longer THRN (P<0.001) when compared to non-smoker males. Age at ophtalmopathy onset was significantly lower in current smokers (34.3±11.7 vs 47.9±13.8, P=0.008), but we found similar percentages of ophtalmopathy between smokers and non-smokers. Smokers >40 years presented higher FT₄ (P=0.049), TT₃ (P=0.032) and FT₄/FT₃ (P=0.034) at diagnosis compared to non-smokers >40. Compared to nonsmokers, current smokers associated higher prevalence of medium/ large goiters (78.6 vs 62.2%, P=0.025). We found no difference between TSH, FT₄, TT₃, FT₃, antibody titer at diagnosis, the THRN and TTRN between current smokers and non-smokers.

Conclusions: Current smoking is associated with younger age at ophtalmopathy onset, larger goiters, and, generally, does not seem to influence hyperthyroidism severity at diagnosis or the time needed until thyroid hormones and TSH levels return to normal.