Circulating miR-146a predicts glucocorticoid response in thyroid eye disease

Objective: Thyroid eye disease (TED) is an immune-mediated disorder of the eye. Intravenous glucocorticoid (GC) is the first-line treatment for patients with active moderate-to-severe TED. However, the response rate is between 50 and 80%. There are still no simple and reliable markers of responsiveness to GC therapy. We aimed to explore the possible role of miR-146a and miR-21 as predictors of responsiveness to GC treatment in TED. Methods: We carried out a prospective longitudinal study on 30 consecutive adult patients with active moderate-to-severe TED and eligible for GC therapy. All patients received the standard GC treatment with methylprednisolone iv. In cases of progressive worsening of Gorman Score for diplopia or with duction restriction <30° in at least two consecutive controls patients also underwent orbital radiotherapy. Response to GC treatment was defined as a decrease of 2 or more points in the clinical activity score (CAS) or CAS <4/10 at 24 weeks. Circulating miRNAs were extracted from patients' serum and quantified by real time PCR. Results: Twenty-three (77%) patients responded to GC. Thyroid surgery, higher CAS, greater proptosis and higher pre-treatment circulating levels of miR-146a emerged as predictive factors of responsiveness to GC. A ROC analysis revealed that miR-146a could predict responsiveness to GC with a positive predictive value of 100%. Conclusion: This is the first study investigating the role of pre-treatment circulating miR-21 and miR-146a to predict responsiveness to GC in TED. miR-146a emerged as a simple, objective, new marker of GC sensitivity that could be used to avoid ineffective administration of GC therapy to TED patients.