Endocrine Abstracts

Introduction: Alemtuzumab is humanized monoclonal antibody used in the treatment of relapsing–remitting multiple sclerosis (MS). The 5year incidence of thyroid adverse events in phase-3 clinical trials is up-to 40.7%. In most cases, the thyroid dysfunction is mild and easily manageable. Hyperthyroidism, particularly Graves’ disease (GD) is more common. We describe a case of unusual thyroid dysfunction in a patient treated with Alemtuzumab.

Case: A 30years old female diagnosed with relapsing-remitting MS at the age of 15yr was initially treated with Natalizumab. She conceived and was off treatment between November 2014 and April 2016. She was commenced on Alemtuzumab in April 2016. In October 2017 she had routine follow-up Thyroid function tests (TFT) which showed supressed TSH <0.02 mIU/L, normal free T4 (fT4) and free T3 (fT3) at 19.1pmol/L and 6.6 pmol/L respectively suggesting subclinical hyperthyroidism. As she was asymptomatic, monitoring was continued. Repeat TFT’s in a months’ time showed TSH=11.32 mIU/L and fT4=5.8 pmol/L suggesting overt hypothyroidism. Thyroid peroxidase antibodies=61.7 (0–34) and TSH receptor antibodies>40. She was subsequently commenced on Levothyroxine 75 mcg OD. Repeat TFT’s after 3weeks revealed TSH=0.09 mIU/L and fT4=37.5 pmol/L. Levothyroxine dose was reduced to 25 mcg OD. Further interval testing showed TSH<0.02 mIU/L and fT4=39.4 pmol/L; hence Levothyroxine was stopped. Isotope uptake scan showed increased (6.5%) uniform uptake suggesting GD. Subsequent TFT’s 2weeks later showed overt thyrotoxicosis with TSH<0.02 mIU/L, fT4=56.8 pmol/L and fT3=29.3 pmol/L. At this stage, she was symptomatic and so commenced on Propylthiouracil 150 mg BD and Propranolol 10 mg TDS. Clinically she improved and recent TFTs showed TSH=0.11 mIU/L, fT4=13.5 pmol/L and fT3=7 pmol/L.

Conclusion: Thyroid dysfunction is the commonest autoimmune disease in patients treated with Alemtuzumab for relapsing-remitting MS. GD being the most common subtype. Our patient initially had a hypothyroid phase subsequently converting into hyperthyroidism, which is uncommon.