Multiple sclerosis, interferon beta and clinical thyroid dysfunction

The objective of this study was to investigate frequency and presentation of clinical thyroid dysfunction in patients treated with interferon beta (IFN-beta). We have collected the cases of clinical thyroid dysfunction in 700 consecutive patients receiving IFN-beta for multiple sclerosis (MS). Five patients (four women, one man) treated with IFN-beta1b developed hyperthyroidism. Three of them have secondary progressive MS, and two have relapsing-remitting MS. It was necessary to stop IFN-beta in three cases; these patients still require carbimazole after several months. In the two other cases, hyperthyroidism disappeared spontaneously. Two patients (one man and one woman) treated with IFN-beta1a developed hypothyroidism. One of them required L-thyroxine. Lastly, an increased thyroid volume without modification of thyroid hormones plasma levels was discovered in a patient receiving IFN-beta1a. Among patients treated with IFN-beta, clinical thyroid dysfunction is much rarer than laboratory thyroid dysfunction. However, this side-effect is sometimes severe.