BACKGROUND
Graves’ disease is the most common cause of hyperthyroidism in the United States. It affects most commonly younger women. Graves’ disease is an autoimmune disorder, meaning that it is caused by antibodies that get confused and attack the thyroid, turning it on and causing the thyroid to be overactive. There are three ways to treat Graves’ disease: 1) surgical removal of the thyroid gland, 2) destroying the thyroid with radioactive iodine therapy or 3) antithyroid medications (Methimazole and PTU). Surgery and radioactive iodine therapy are considered “definitive therapy” because they treat hyperthyroidism by causing permanent hypothyroidism, which is then managed with thyroid hormone therapy. In contrast, antithyroid medications are given with the goal of causing the Graves’ disease to go into remission, allowing the medications to be stopped and the thyroid function to return to normal.

Because there is a wide range in the severity of Graves’ disease and the response to medications, identifying clinical factors that may predict remission with medications can help guide doctors and patients when deciding on the most appropriate therapy for each individual. This study was done to investigate how age and sex of patients affect the severity of the Graves’ disease, the chances of achieving remission and the risk of recurrence once treatment is stopped.

THE FULL ARTICLE TITLE
Suzuki N et al. Does Age or Sex Relate to Severity or Treatment Prognosis in Graves’ Disease? Thyroid Epub 2021 Apr 21. PMID: 33882721.

SUMMARY OF THE STUDY
This study was done by reviewing data from patients who were retrospectively identified as newly diagnosed with Graves’ Disease at Ito Hospital in Japan from January 2005 to June 2019. Graves’ disease was diagnosed by the presence of hyperthyroidism with positive antibodies or an elevated thyroid scan result.

Data collected included free T4 and free T3 levels, along with thyroid gland volume (obtained by ultrasound). Patients were grouped into 10-year age groups, ranging from 10-19 years (10’s), 20-29 years (20’s) and so on. The patients younger than 10 and older than 80 were excluded because there were small numbers in each group.

A group of 2749 patients (2244 females, 505 males) diagnosed with Graves’ disease between January 2009 and December 2020 with available data for follow up of 12 months or more were chosen for analysis of prognosis. Within this group, 2191 were treated with antithyroid medications. These medications were discontinued if the serum TSH was within normal range for > 6 months on a very low dose of antithyroid medications. Remission was defined as maintaining normal thyroid hormone levels for > 1 year after stopping the medications.

In this Japanese group of patients studied, men were found to have higher severity of hyperthyroidism due to Graves’ disease, with higher serum thyroid hormone concentrations and larger thyroid volumes. Severity of hyperthyroidism declined with age in both sexes. A total of 1187 (53%) of women achieved remission after a course of antithyroid medications as compared to 204 (40%) of men. Younger patients had a higher risk of recurrence. Sex and smoking did not have a significant effect on the risk for recurrence.

WHAT ARE THE IMPLICATIONS OF THIS STUDY?
This study shows that the likelihood of remission of Graves’ disease after a trial of antithyroid medications is higher than expected and is more common in women and less common in younger patients. One limitation of the study is that the Japanese diet contains a lot of iodine which likely impacts dose of medications required and rates of remission. However, this study is important for patients because it adds more information about treatment response and chances for remission. It helps empower patients and doctors when deciding on the most appropriate treatment for each individual.

— Jessie Block-Galarza, MD

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