Hypothyroidism in Vasculitis.

Objective To study the prevalence, risk and clinical associations of hypothyroidism among several forms of vasculitis. Methods Patients with giant cell arteritis (GCA), Takayasu arteritis (TAK), polyarteritis nodosa (PAN), and the three forms of ANCA-associated vasculitis (AAV, granulomatosis with polyangiitis (GPA), microscopic polyangiitis (MPA), and eosinophilic granulomatosis with polyangiitis (EGPA) enrolled in a prospective, multicentre, longitudinal study were included. Results The study included data on 2,085 patients, 63% female, 90% White, mean age 54.6 (±17.2) years. Diagnoses were: GCA (20%), TAK (11%), PAN (5%), GPA (42%), MPA (8%), and EGPA (14%). Hypothyroidism was present in 217 patients (10%), 83% female, mean (±SD) age 59.8 (14.5) years.Age- and sex- adjusted, risk of hypothyroidism was: GCA (OR 0.61, 95% CI 0.41, 0.90), TAK (OR 0.57 95% CI 0.31, 1.03), PAN (OR 0.59 95% CI 0.25, 1.38), GPA (OR 1.51 95% CI 1.12, 2.05), MPA (OR 1.81, 95% CI 1.18, 2.80) and EGPA (OR 0.82, 95% CI 0.52, 1.30). Among patients with AAV, age- and sex- adjusted risk of hypothyroidism was higher with positive myeloperoxidase (MPO-ANCA) (OR 1.89, 95% CI 1.39, 2.76). The clinical manifestations of vasculitis were similar in patients with and without hypothyroidism except transient ischemic attacks which were more frequently observed in patients with GCA and hypothyroidism (12% vs 2%, p 0.001). Conclusions Differences in the risk of hypothyroidism among vasculitides may be due to genetic susceptibilities or immune responses. This study confirms an association of hypothyroidism with MPO-ANCA.