DYSPNEA, LUNG-FUNCTION AND RESPIRATORY MUSCLE PRESSURES IN PATIENTS WITH GRAVES-DISEASE

To understand the pathophysiology of dyspnoea in patients with hyperth yroidism, lung function, maximum inspiratory, expiratory respiratory m uscle pressures (MIP and MEP) and intensity of dyspnoea (after six min utes walking test) were recorded in 12 consecutive patients with activ e Graves' disease. Reassessment was done after achieving euthyroidism with 8-12 wk of carbimazole therapy. Patients covered similar distance during 6 min walking before and after carbimazole therapy. However, t here was a significant reduction in dyspnoea following euthyroidism. T his was accompanied by significant decrease in respiratory rate, minut e ventilation, forced expiratory volume in one second (FEV1%) and impr ovement in the forced vital capacity (FVC). No significant changes in tidal volume (TV) and maximum-midexpiratory flaw rates (MMEFR), MIP an d MEP were observed. Lung function parameters, MIP and MEP did not cor relate with the severity of dyspnoea. Serum T4 levels correlated inver sely with the distance covered during 6 min walking test, MIP and MEP. To conclude, increased breathing effort in presence of reduced FVC ma y lead to dyspnoea during hyperthyroid phase in patients with active G raves' disease. Lack of correlation between the severity of dyspnoea a nd abnormalities in lung function suggests that other mechanisms of dy spnoea may also operate in these patients.