Effect of 1-year treatment with interferon-beta 1b on thyroid function andautoimmunity in patients with multiple sclerosis

Objective: Interferon-beta (IFN-beta) is a widely used therapy for multiple sclerosis (MS), a demyelinating disease of the central nervous system. Thi s study has evaluated the effect on thyroid function and autoimmunity of a I-year treatment with IFN-beta 1b in patients with MS. Patients: We studied 31 patients (age 34 +/- 7 years, 21 women) with relaps ing-remitting MS during IFN-beta 1b treatment of I year duration, Systemati c thyroid assessment and measurements of serum interleukin-6 (IL-6) levels were performed at baseline and every 3 months during treatment. Results: Sixteen percent of the patients had autoimmune thyroiditis before IFN-beta 1b, all positive for anti-peroxidase antibodies. The overall incid ence of thyroid dysfunction was 33% over 1 year (10% hyperthyroidism, 23% h ypothyroidism). Thyroid autoimmunity developed in 5/26 patients (19%), in o ne case without dysfunction. In addition to autoantibody positivity at base line, female gender and the presence of an ultrasound thyroid pattern sugge stive of thyroiditis were identified by multiple logistic regression as add itional risk predictors for the development of thyroid dysfunction. During IFN-beta 1b treatment, serum IL-6 levels rose in a consistent biphasic patt ern: there was, however, no difference between patients with or without inc ident thyroid abnormalities. Conclusions:We conclude that IFN-beta 1b therapy can induce multiple altera tions in thyroid function, some of which are unrelated to thyroid autoimmun ity. IL-6 measurement is not useful to identify patients prone to develop t hyroid abnormalities. Though thyroid dysfunction is generally subclinical a nd often transient, systematic thyroid assessment should be performed durin g IFN-beta 1b treatment.