Thyroid disease common within 5 years of AAV diagnosis, study finds
Excessive or insufficient hormone production affects some 20% of patients
About 1 in every 5 people with ANCA-associated vasculitis (AAV), at some point in life, may experience problems that keep the thyroid gland from making the right amount of hormones, with these problems most often developing within five years of an AAV diagnosis, a large study found.
While thyroid disease appears to be more common in people with AAV than the general population, no factors were identified that could predict its development, suggesting all patients should have regular thyroid tests, the researchers noted.
Studies on how AAV and thyroid disease interact over time may improve “our understanding of the co-occurrence of these diseases,” they wrote, to “shed light on a common or overlapping causative pathway and suggest appropriate therapies.”
The study, “Thyroid disease in ANCA-associated vasculitis: a clinical and epidemiological study,” was published in RMD Open.
Thyroid disease can appear as hypothyroidism or hyperthyroidism
The thyroid is a butterfly-shaped gland located in the neck. The hormones it makes control many bodily functions, such as weight and appetite, heart beat, and blood pressure. Sometimes, the thyroid makes too little or too much hormones, a condition known as thyroid disease.
Thyroid disease can be divided into two main types: hypothyroidism, which occurs when the thyroid is underactive and makes too little hormones, and hyperthyroidism, when it’s overactive and releases more hormones than are needed.
Having an autoimmune disease increases the risk of thyroid disease. Earlier studies found that thyroid disease appears to be common in AAV, which occurs when self-reactive antibodies drive immune cells to launch an inflammatory attack that damages small blood vessels, causing disease symptoms.
To study the clinical features of people with both AAV and thyroid disease, and to find what may predict the development of thyroid disease, the researchers combined data from two groups of patients in southern Sweden and in Cambridge, U.K.
Data came from a total of 644 people with AAV: 319 (49.5%) who had granulomatosis with polyangiitis (GPA), 300 (46.5%) with microscopic polyangiitis (MPA), and 25 (4%) with eosinophilic granulomatosis with polyangiitis (EGPA). GPA, MPA, and EGPA are three types of AAV.
End-stage kidney disease less common when thyroid disease precedes AAV
Before an AAV diagnosis, 100 (15.5%) of these patients had been diagnosed with thyroid disease. The most frequent type of this disease was hypothyroidism, followed by hyperthyroidism, goiter (an enlarged thyroid), and thyroiditis (an inflamed thyroid).
Compared to patients without thyroid disease, those with it were more likely to test positive for antibodies against myeloperoxidase (MPO), which are known causes of AAV, and to be female. They also had lower levels of C-reactive protein, a marker of inflammation, and experienced fewer general AAV symptoms.
After being diagnosed with AAV, 29 (5.3%) of the 544 remaining patients developed thyroid disease within a median 3.2 years. Most, about two-thirds (69%), developed thyroid disease within five years of their AAV diagnosis.
During the entire follow-up period, 92 patients (14%) developed end-stage kidney disease, a common AAV complication due to damage to small blood vessels in the kidneys.
End-stage kidney disease tended to be less common in patients with prior thyroid disease than other patients (8% vs. 15%). Having thyroid disease before an AAV diagnosis also was linked to better kidney survival — typically, no progression to kidney failure — after adjusting for factors such as age and the presence of anti-MPO antibodies.
The number of new cases of thyroid disease in AAV was “higher than has been reported in the general population,” the researchers wrote. However, no factors were identified that could predict its development in these patients.
A dual diagnosis “should be taken into consideration in patients with AAV who suffer non-specific manifestations such as fatigue that could be attributed to [thyroid disease] as well as to AAV,” the researchers concluded, while suggesting more studies into how AAV and thyroid disease interact over time.
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