Liver and thyroid function and autoimmunity during interferon-β1b treatment for MS

Background: The occurrence or recurrence of autoimmune diseases or of autoantibodies (autoAb) has been reported during type I interferon (IFN) treatment. Objective: To define the frequency of thyroid and liver dysfunction and of autoimmunity during IFN-beta 1b (IFNB) treatment of MS. Methods: Prospective 1-year multicenter follow-up of 156 patients with MS recruited by 18 centers was conducted. Thyroid-stimulating hormone and anti-thyroid autoAb were measured by an immunoradiometric method, thyroid hormones by chromatographic assay, and non-organ-specific autoAb by indirect immunofluorescence. Tests were repeated every 3 months. The probability of having liver, thyroid, or autoAb alterations was analyzed longitudinally with the generalized estimating equations (GEE) method. Results: Thyroid dysfunction was observed in 5.3% of cases at baseline and 8.3% de novo during IFNB treatment. GEE analysis showed that the probability of having thyroid alteration did not change significantly during treatment compared with baseline. Liver alteration was observed in 4.6% of cases at baseline and 37.5% de novo during IFNB treatment (p < 0.0001). GEE analysis showed that the probability of having liver alteration was higher (p < 0.002) at months 3 and 6 compared with baseline, returning to values similar to baseline by month 9. AutoAb were detected in 16.1% of patients at baseline and in 20% during IFNB. GEE analysis showed that the probability of having autoAb did not change significantly during treatment compared with baseline. Thyroid or liver alteration or autoAb occurring de novo during IFNB were usually transient. Conclusions: Differently from the frequency of liver function alteration (which significantly increased during the first months of IFNB treatment, suggesting a probable causal relationship with IFNB), the frequency of thyroid dysfunction or of autoimmunity showed random and insignificant changes over time, probably not related to IFNB treatment.