AAV Patients More Likely to Develop Thyroid Disease, Korean Study Finds

ANCA-associated vasculitis patients in Korea have a high prevalence of thyroid dysfunction, with the condition affecting mainly those who are older, have ANCA antibodies, or renal involvement at diagnosis, a study has found.

The study, “Thyroid Dysfunction in Patients with Antineutrophil Cytoplasmic Antibody−associated Vasculitis: A Monocentric Retrospective Study,” was published in The Journal of Rheumatology.

Research suggests that patients with ANCA-associated vasculitis (AAV) have a higher prevalence of thyroid disease than the general population. However, whether this association is seen in patients across the globe is unknown.

A team of researchers assessed the prevalence of thyroid disease in AAV patients in Korea. They reviewed the medical records of 186 patients with AAV followed at the Department of Rheumatology, Yonsei University College of Medicine, Severance Hospital in Korea, from October 2000 to July 2018.

The thyroid is responsible for producing the hormones thyroxine (T4) and triiodothyronine (T3), which play important roles in body function. Another hormone, called thyroid-stimulating hormone (TSH) is produced by the pituitary gland; its role is to stimulate the thyroid gland to produce thyroid hormones.

In the study, patients were deemed as having hyperthyroidism (an overactive thyroid gland) if they produced low levels of TSH, and if T3 levels were within normal levels. Subclinical hypothyroidism (a poorly functional thyroid gland) was defined when TSH levels were increased and levels of T4 were normal.

Overall, 27 patients (14.5%) had thyroid disease, including seven who already had thyroid problems before getting an AAV diagnosis.

Compared to the general Korean population, AAV patients had a significantly higher prevalence of overt hyperthyroidism (0.5% vs. 5.4%) and hypothyroidism (0.7% vs. 4.3%).

The prevalence of subclinical (not showing symptoms) hyperthyroidism was lower in AAV patients than the general population — 1.6% vs. 3.0%. But subclinical hypothyroidism was similar in both groups – 3.2% vs. 3.1%.

Moreover, when researchers compared patients with and without of thyroid disease, they observed that those with thyroid dysfunction were more frequently diagnosed with MPO-ANCA.

AAV patients with thyroid disease also developed kidney and heart disease more commonly than those with normal thyroid function.

The team also estimated that patients with MPO-ANCA (myeloperoxidase ANCA) and with a 2009 five-factor score, which measures prognosis at diagnosis in AAV patients, above or equal to 2 developed thyroid dysfunction sooner.

Predictors of thyroid disease in AAV patients included being older than 65, ANCA-positivity, and impaired renal function at the time of AAV diagnosis.

“This study is a pilot study to first discover the prevalence and the predictors at diagnosis of thyroid dysfunction in Korean patients with AAV,” researchers wrote.

“Results of thyroid function tests will provide more reliable and validated information on the clinical implication of thyroid dysfunction in patients with AAV,” they concluded.