Effect of radioactive iodine therapy on lacrimal gland functions in patients with hyperthyroidism

Radioactive iodine (RAI) therapy is preferred in the treatment of hyperthyroidism because of its effectiveness, noninvasiveness, and low costs. I has been detected in extrathyroidal tissues, such as in gastric mucosa, salivary glands, and lacrimal glands. To the best of our knowledge, there is no publication concerning the effects of RAI therapy for hyperthyroidism on tear production. In the present study, we evaluated whether or not the lacrimal glands are affected after RAI therapy when compared with pretreatment period.

The Schirmer and tear break-up time (TBUT) tests were used to assess 32 eyes of 16 patients with conditions that were diagnosed as hyperthyroidism before and at 3 and 6 months after RAI treatment. In addition, pretreatment values of patients were compared with that of controls. It was evaluated whether or not a correlation exists between the results and the dose or iodine uptake values.

There was no significant difference between pretreatment values of Schirmer and TBUT tests obtained in the patient group and those of the control group (P > 0.05). In the patient group, there was a significant difference between the posttreatment and pretreatment values (P < 0.05). There was a positive correlation between uptake values obtained at 24 hours and the values obtained by TBUT and Schirmer tests on both eyes at 3 and 6 months. At 6 months, the uptake value at 24 hours was 28.83 ± 60 for both eyes in patients with TBUT test values less than 10, whereas it was 39.25 ± 7.88 for the right eye and 39.00 ± 6.85 for the left eyes in patients with TBUT test values greater than 10. The difference was statistically significant (P < 0.05).

In our study, we concluded that the decrease in mucin and aqueous production occurs due to affected lacrimal glands by RAI therapy; however, this effect is not dose dependent.