Changes in pulmonary ventilatory function in patients with thyrotoxicosis

Kim, Won Bae; Chung, Hyun Kyung; Lee, Sun Hwa; Moon, Byung Sool; Lee, Jae Ho; Park, Do Joon; Cho, Bo Youn; Chung, Hee Sooh

Abstract

OBJECTIVE
Dyspnea is a common symptom in patients with thyrotoxicosis, which may be caused by several mechanisms including pulmonary ventilatory dysfunction. There have been controversies among studies on changes in pulmonary ventilatory function in thyrotoxicosis. We were to evaluate the changes in pulmonary ventilatory function in patients with thyrotoxicosis.
METHODS
We measured the pulmonary ventilatory function with spirometry in 32 thyrotoxic patients with Graves' disease and in 22 age, sex-matched euthyroid control subjects. The changes in ventilatory function after treatment were evaluated in 18 thyrotoxic patients who became euthyroid with antithyroid drug treatment.
RESULTS
1) Forced vital capacity(FVC) was significantly lower in thyrotoxic patients compared to control subjects(3.06+/-0.68 L and 3.35+/-0.55 L, respectively, p<0.05). Percent predicted values of FVC showed similar results; 82+/-16 % in patients and 95+/-11 % in control subjects(p<0.05).2) Forced expiratory volume for 1 sec.(FEV1.0), forced expiratory flow 25-75(FEF 25-75) and FEF 50 were not different between patients and control subjects. FEV1.0/ FVC ratio were higher in thyrotoxic patient than in control(88+/-7 % vs. 84+/-8 %, p<0.05). 3) Serum thyrotropin binding inhibitor immunoglobulin (TBII) activities were significantly correlated with pretreatment FVC values(R=-0.45, p<0.05) and with FEV1.0 values(R=-0.41, p<0.05) in thyrotoxic patients. However, serum thyroid hormone concentrations had no correlations with FVC or with FEV1.0 values. 4) FVC, FEV1.0 of thyrotoxic patients increased, and FEV1.0/FVC ratio decreased sifnificantly after treatment of thyrotoxicosis in patient group. Numbers of patients with normal, mild, moderate, severe restrictive disease were 10, 4, 3, 1, respectively before treatment, which became 14, 2, 2, 0 after treatment of thyrotoxicosis in patient group.
CONCLUSION
Ventilatory disturbances of restrictive pattern were common in thyrotoxic patients that were partially reversible after treatment of thyrotoxicosis. Such changes may be one of mechanisms causing dyspnea in thyrotoxic patients. The fact that decrease in FVC were significantly associated with serum TBII activities (thyroid autoantibody), but not with degree of thyrotoxicosis suggests that autoimmune process itself is involved in the development of pulmonary function abnormalities observed in those patients.