R. Guleria et al., DYSPNEA, LUNG-FUNCTION AND RESPIRATORY MUSCLE PRESSURES IN PATIENTS WITH GRAVES-DISEASE, INDIAN JOURNAL OF MEDICAL RESEARCH, 104, 1996, pp. 299-303
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.