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Impaired cardiopulmonary exercise capacity in patients with hyperthyroidism
G Kahaly1, J Hellermann, S Mohr-Kahaly
1Department of Medicine III (Endocrinology/Metabolism), Johannes-Gutenberg-University Hospital, Mainz, Germany.
Chest
|January 1, 1996
Summary
Hyperthyroidism significantly reduces exercise tolerance by impairing heart rate response during exertion. These deficits in cardiopulmonary function are reversible once thyroid levels normalize.
Area of Science:
- Cardiology
- Endocrinology
- Exercise Physiology
Background:
- Hyperthyroidism is linked to decreased exercise tolerance.
- Respiratory gas exchange analysis, a noninvasive measure of cardiopulmonary capacity, has not been extensively studied in hyperthyroid patients.
Purpose of the Study:
- To evaluate cardiopulmonary exercise capacity in hyperthyroid patients using respiratory gas exchange analysis.
- To determine if exercise capacity impairments are reversible with treatment.
Main Methods:
- Cardiopulmonary exercise testing was performed on 12 women with Graves' hyperthyroidism (H) and 18 euthyroid (E) control subjects.
- The ventilatory anaerobic threshold was determined using the V-slope method.
- Echocardiography was used to assess cardiac function at rest.
Main Results:
- Hyperthyroid patients exhibited higher resting heart rates and a blunted heart rate increase during exercise compared to euthyroid controls.
- Work rate and anaerobic threshold were reduced in hyperthyroid patients.
- Echocardiography revealed increased ejection fraction and cardiac index in hyperthyroid patients, suggesting altered cardiac function.
Conclusions:
- Respiratory gas exchange analysis reveals significant, reversible alterations in cardiopulmonary exercise capacity in hyperthyroid patients.
- Impaired chronotropic response during exercise is a likely primary factor limiting work capacity in hyperthyroidism.