In Reply: We agree with Drs Shin and Lee that smoking may influence the course of Graves disease by modulating immune function. Levels of soluble IL-2 receptor, a marker of T-cell activation, have been shown to correlate positively with the activity of Graves disease, and smokers appear to have higher concentrations of soluble IL-2 receptor than nonsmokers.
However, these relationships have not been adequately studied and are likely to be more complex. In particular, it is unclear whether the association between Graves disease and circulating soluble IL-2 receptor concentration reflects the underlying autoimmune activity or, as some studies have suggested, is mediated by the hyperthyroidism. In the latter case, hyperthyroidism of any cause would elevate soluble IL-2 receptor concentration while hypothyroidism would have the opposite effect.1- 3 We agree that further research is needed to fully address these unanswered questions.