Effects of antithyroid medication on the flow-volume loop in patients with hyperthyroidism

This prospective study was designed to evaluate the effects of hyperthyroidism on flow-volume loops in nonasthmatic 20 patients with hyperthyroidism. Thyroid related hormones (Total T3, Total T4 and TSH), thyroid gland volumes with ultrasonography, circumference of neck values and flow-volume loops were obtained at the beginning and after three months of antithyroid treatment. Propylthiouracil treatment was followed by a statistically significant decrease in thyroid gland volume and circumference of neck (p< 0.001 and p< 0.001, respectively). The most significant result was improvement of maximum midexpiratory flow rate (MMEFR) after propylthiouracil therapy for three months (p= 0.003). Increases in mean forced expiratory flow after 25% of FVC has been exhaled (FEF25), mean forced expiratory flow after 75% of FVC has been exhaled (FEF75) values were found consistent with the overall improvement in expiratory flow parameters (p= 0.044, p= 0.012 respectively). In conclusion, we speculated that improvement of expiratory flow parameters might be the earlier changes in flow volume loops of patients who were treated with propylthiouracil for hyperthyroidism.