Impact of subclinical hypothyroidism in cardiopulmonary response during effort and its recovery

In order to identify the characteristics of subclinical hypothyroidism (SH) during physical stress and its recovery, 15 SH patients and 16 healthy women were compared by a treadmill cardiopulmonary test. Means of variables were analyzed by the Mann-Whitney U test. Patients obtained lower values for peak expired fraction Of 02 (14.90 +/- 1.05 x 16 +/- 1.14%; p = 0.014); systolic blood pressure variation (34.33 +/- 17.92 x 52.50 +/- 17.22; p = 0.009); exercise duration (8.83 +/- 2.91 x 14.5 +/- 5.63 min; p = 0.0005), maximal test load (11.6 +/- 4.22 x 18.94 +/- 5.45%; p = 0.0004), as well as tendencies in gas exchange ratio and peak heart rate. Between the first and the third recovery minutes, there was a reduction of only 0.71 mmHg in the diastolic blood pressure, whereas there was a 5.33-mmHg reduction to control group (p = 0.0009) (slower recovery of patients). It is presumable that SH may cause cardiopulmonary dysfunctions, with higher sensibility to the parameters previously cited.