BACKGROUND
Graves’ disease is one of the most common causes of an overactive thyroid gland (hyperthyroidism). In Graves’ disease, the patient’s immune system produces high levels of antibodies to the TSH receptors (TRAb). TRAb then binds to the TSH receptor on the thyroid gland and stimulates it to increase thyroid hormone production. Graves’ disease can be treated with antithyroid drugs (ATDs – Methimazole or PTU), radioactive iodine or surgery. ATDs can be used either in the short term to prepare patients for either radioactive iodine or surgery or as a long term treatment. When used as a long term treatment, the goal of ATDs is to cause the Graves’ disease to go into remission, usually associated with the TRAb levels declining or going away. Once the ATDs are stopped, there can be anywhere from a 5-90% risk of relapse of the Graves’ disease. Some of the risk factors that have been associated with increased risk of recurrence include: younger age, male sex, a large thyroid gland, severe hyperthyroidism at diagnosis, cigarette smoking and high TRAb levels at diagnosis or at the end of ATD treatment. This study was done to study possible association between the level of TRAb at diagnosis of Graves’ disease and severity of hyperthyroidism and risk of recurrence after stopping ATD treatment.

THE FULL ARTICLE TITLE:
Bano A et al 2019 Age May Influence the Impact of TRAbs on Thyroid Function and Relapse-Risk in Patients with Graves Disease. J Clin Endocrinol Metab 104(5):1378-1385.

SUMMARY OF THE STUDY
A total of 384 patients with Graves’ disease (average age 48 years, 85.2% women, and 93.5% White) were included in the study from an endocrine clinic in England. All patients has thyroid levels and TRAb levels measured. If TRAb levels were not high, patients had a thyroid scan to confirm the diagnosis of Graves’ disease. None of the patients in the study were taking other medications that can affect thyroid levels or were pregnant.

A total of 231 patients were included in the study of risk of recurrence. Patient were treated with ATD for an average of 12 months. These patients were followed up to 12 months after stopping ATD treatment, with range of follow-up from 3 to 12 months.

A higher TRAb level at diagnosis was associated with higher thyroid hormone levels at diagnosis. This association was different in younger and older patients. In patients aged 55 years or older, a higher TRAb level was associated with higher thyroid hormone levels only if TRAb levels were below 10 U/L. In those with TRAb above 10 U/L, there was no association between TRAb level and thyroid hormone levels.

There was 5% increased risk of recurrence for every 1 unit increase in TRAb level at diagnosis in the whole group. Again, this association was different in younger and older patients. In patients aged 18-41 years, there was 13% increased risk of recurrence for every 1 unit increase in TRAb level at diagnosis. In patients aged 42-56 years, there was 5% increased risk of recurrence for every 1 unit increase in TRAb level at diagnosis. However, in patients aged 56 years or older, there was no association between TRAb level at diagnosis and risk of recurrence.

WHAT ARE THE IMPLICATIONS OF THIS STUDY?
Higher TRAb levels at the diagnosis of Graves’ disease were associated both with higher thyroid hormone levels at diagnosis and an increased risk of recurrence within 12 months of stopping ATD treatment in patients aged less than 55 years. In older patients with Graves’ disease, TRAb level at diagnosis may not be a good marker of risk of recurrence. Therefore, decision on how often and how long to follow older patients after stopping ATD treatment for Graves’ disease may be different than in younger patients.

— Sun Y. Lee, MD

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