The influence of radioiodine therapy on ocular changes and their relation to urine cotinine level in patients with Graves' Ophthalmopathy.

OBJECTIVES: Radioiodine therapy (RIT) is frequently used as the definitive treatment in patients with Graves' hyperthyroidism when remission is not achieved with anti-thyroid drugs (ATDs). In this observational study, we intended to examine whether the use of high doses of radioiodine (RAI) [22 mCi (814 MBq)] with prophylaxis of oral glucocorticoids (oGCS) does not exacerbate Graves ophthalmopathy (GO) in smokers and non-smokers, especially regards to the urine level cotinine and ocular changes before and after RIT.

PATIENTS AND METHODS: The studied group consisted of 26 smokers, aged 28-61 years and 25 non-smoker patients, aged 21-54 years, respectively. The patients were enrolled to RAI after one-year of ineffective ATDs treatment. Criterion for inclusion in the study were patients with mild GO with hyperthyroidism at diagnosis based on the severity (NOSPECTS) and activity (CAS) scale. All the patients were subjected to RIT with oGCS prophylaxis and evaluated prospectively during a one-year follow-up. The ophthalmological examination was performed at various stages of RIT: initial pre-radioiodine administration, at the time of treatment 6, and 12 months after RAI. The present study is unique, because the urine cotinine measurement was employed to detect nicotine exposure, also in regard to smoking intensity.

RESULTS: In smokers, the values of serum TPO-Abs were statistically significant in the second and six month (p<0.05) and in the second and after one year (p<0.005). The TSHR-Abs concentration was significantly higher in smokers (p<0.05), rising from 22.9±1.2 IU/L before therapy to 29.6±5.3 IU/L - 2 months, 32.6±8.6 IU/L - 6 months, and slightly decreased 28.9±10.6 IU/L - 12 months. These observed changes were statistically different between groups at baseline (p<0.05) and after one-year of follow-up (p<0.005). Mean urine cotinine were considerably higher in smokers comparing to non smokers in each point of observation [903.4±770.0 and 5.2±1.7 ng/mL at baseline (p<0.001), 412.8±277.3 and 3.0±0.6 ng/mL after 2 months (p<0.001), 452.0±245 and 6.6±3.6 after 6 months (p<0.001), 379.4±236.8 and 1.0±1.2 after one year (p<0.001)]. The CAS values in the smoking group before RIT increased statistically from 2.8±0.2 points at baseline to 4.3±0.3 after 6 months, and 4.0±0.5 (12 months), while in the non-smoking patients it was 1.4±0.2, 2.8±0.3 and 2.2±0.2, respectively. The level of urine cotinine correlated positively with CAS and TSHR-Ab in the smoking group (r=0.41; p<0.05) at baseline and during follow-up (2 months: r=0.46; p<0.001, 6 months: r=0.47, p<0.005; 12 months: r=0.46; p<0.005). In the NOSPECS classification, the symptoms changed from mild to moderate, mostly in smoking patients.

CONCLUSIONS: 1) ablative RIT dose with prophylactic oral prednisone is a safe treatment in both smokers and non-smokers with mild GO; 2) The post hoc analysis showed that urinary level of cotinine can be very helpful in the assessment of exacerbation of ophthalmological clinical symptoms before and after RIT particularly in smokers.