Our aim was to review our MS teams’ monitoring of TFTs during and after treatment with alemtuzumab. We wanted to summarise the incidence and characterise the nature of thyroid dysfunction (TD) in our Northern Ireland cohort. 

Three clinical trials in active relapsing remitting multiple sclerosis demonstrate superior clinical efficacy for alemtuzumab versus interferon beta-1a^1,2,3. A reported side effect of alemtuzumab is thyroid autoimmunity⁴. It is estimated that approximately 35% of patients treated with alemtuzumab will develop TD, with a peak incidence at 36 months⁵. It is recommended that thyroid function tests (TFTs) checked every 3 months during treatment and for 48 months following treatment completion⁶. 

We searched the Northern Ireland Disease Modifying Treatment database for all patients receiving alemtuzumab. Patients were identified and data was collected retrospectively from clinical records. Data collected included dates of alemtuzumab treatment, TFT monitoring, subsequent follow up and treatment required.

171 patients received alemtuzumab between 2015 and 2019 in Northern Ireland. Twenty-three cases had abnormal baseline TFTs, pre-treatment. Of 148 patients with normal baseline TFTs, 34 (23%) experienced TD following treatment, mean follow-up 23 months. 65% were initially noted to be hyperthyroid whilst 35% were hypothyroid. Many patients fluctuated between dysthyroid states, in some cases without any treatment. 100% of patients were referred to Endocrinology and 88% of them received medical management. One patient underwent thyroidectomy. There were no cases of Grave’s ophthalmopathy. 58% patients were positive for anti-TPO antibody or TSH receptor antibody (or both) suggesting an autoimmune reaction like Grave’s disease or thyroiditis.

The frequency of alemtuzumab-induced TD in our cohort was similar to that reported in the literature. The nature of TD varied, and many patients fluctuated between dysthyroid states. This data highlights the importance of close surveillance for thyroid dysfunction due to the risk of complex, late-onset autoimmunity.