Airway response to inhaled salbutamol in hyperthyroid and hypothyroid patients before and after treatment

For many years the development of thyrotoxicosis has been known to cause a deterioration in asthma but the mechanism is unknown. We have studied the effect of thyroid function on airway beta adrenergic responsiveness in 10 hyperthyroid and six hypothyroid subjects before and after treatment of their thyroid disease. Airway adrenergic responsiveness was assessed by measuring specific airway conductance (sGaw) after increasing doses of inhaled salbutamol (10-410 micrograms). After treatment there was no difference in resting FEV1, sGaw, or thoracic gas volume. FVC increased in the hyperthyroid subjects but did not change in the hypothyroid subjects. In the hyperthyroid subjects there was a significant increase in delta sGaw after 35, 60, 110, and 41 micrograms salbutamol; in sGaw after 60, 110, and 410 micrograms salbutamol; and in the area under the salbutamol dose response curve (AUC) after treatment of the thyroid disorder. In the hypothyroid subjects there was a significant reduction in sGaw after 10 and 60 micrograms salbutamol and in the AUC after treatment. When all subjects were considered, there was a negative correlation between the AUC and serum thyroxine values. These findings suggest that an inverse relationship exists between the level of thyroid function and airway beta adrenergic responsiveness.