Does chronic thyroid inflammation explain persistent symptoms in Hashimoto thyroiditis?

Around 10% of the female population have Hashimoto thyroiditis as judged by positive thyroid peroxidase antibodies in their blood, and approximately 50% of these people progress to thyroid failure, manifest as thyroid underactivity (hypothyroidism) over several decades. When seen under a microscope, there is progressive destruction of the thyroid cells by inflammatory lymphocyte white blood cells, which are targeted to destroy the thyroid hormone producing cells. Once thyroid underactivity is recognised, the standard treatment is thyroid hormone replacement using levothyroxine tablets. However, about 10% of patients remain dissatisfied with standard levothyroxine treatment, typically leaving fatigue, muscle aches and cognitive symptoms often referred to as 'brain fog'. Multiple randomised clinical trials have shown that improvement in the blood thyroid hormone levels or adding tri-ioidothyronine (T3, the active thyroid hormone) does not help these people. This raises the possibility that the thyroid inflammation itself rather than the consequent hormonal deficiency is responsible for the residual symptoms in hypothyroid patients.

We will perform a double blind, randomised controlled trial of an immunosuppressant/ anti-inflammatory drug called mycophenolate, which will kill off the lymphocytes in the thyroid and reduce the thyroid inflammation. Forty-eight women with Hashimoto thyroiditis will be in the trial for 16 weeks, with thirty taking the active mycophenolate and eighteen taking placebo. The primary outcome measurement will be the change in the number of inflammatory lymphocytes in thyroid samples taken before and after the experimental treatment by fine-needle aspiration. We will also perform a multimodal investigation including fatigue, other symptom and quality of life questionnaires, cognitive tests, blood 'acute-phase' inflammation markers, cytokine assays and functional imaging of the activity of inflammatory cells in the thyroid by FDG-PET. This will demonstrate whether thyroid inflammation can be reduced by mycophenolate and whether this will improve the persistent symptoms and poor QoL for these patients. Mycophenolate is now an inexpensive drug and if successful, this treatment could improve the health of around 100,000 working-age women in the UK who have Hashimoto thyroiditis and who have persistent symptoms during conventional levothyroxine treatment.