Respiratory muscle strength in hypothyroidism.

To investigate respiratory muscle strength in patients with hypothyroidism, global respiratory muscle strength was assessed by measuring mouth pressure during PImax and PEmax efforts. Maximum pressures, VC, FEV1, FVC, T3, T4, and TSH were measured in 43 hypothyroid patients. Measurements were made before and three months after replacement therapy with thyroxine. The results showed that the mean value of PImax and PEmax increased after treatment. Significant change was found in the mean value of VC, FEV1, and FVC after treatment but not in the FEV1/FVC ratio. A highly statistically significant linear relationship was found between PImax and TSH and between PEmax and TSH as well as between PImax and T3 and PEmax and T3. We conclude that hypothyroidism affects respiratory muscle strength and that this weakness is linearly related to thyroid hormone levels. Respiratory muscle weakness is present in both inspiratory and expiratory muscles and is reversible with treatment.

Respiratory muscle strength in hyperthyroidism before and after treatment.

We undertook this study to investigate respiratory muscle strength in relation to thyroid function in 20 thyrotoxic patients and in a group of 20 normal subjects matched for age and sex. Global respiratory muscle strength was assessed by measuring mouth pressure during maximal static inspiratory (PImax) and expiratory (PEmax) efforts. We also measured VC, FVC, and FEV1 as well as thyroid-related hormones (T3, T4, TSH). Measurements were made once in normal subjects and twice in thyrotoxic patients, before and 3 months after medical treatment. Our results showed that both maximal pressures were significantly reduced (p less than 0.0001) before treatment in thyrotoxic patients in relation to the mean values of the normal subjects (p less than 0.0001), and they increased significantly (p less than 0.0003) after treatment. Lung volumes were significantly reduced (p less than 0.0001) before and increased significantly (p less than 0.008) after treatment. The ratio FEV1/FVC did not change. A statistically significant linear relationship was found when PImax of patients with thyrotoxicosis before treatment and of normal subjects were plotted against thyroid hormones (T3, T4) (r = -0.746 and r = -0.745, respectively, p less than 0.001). Similarly, a statistically significant linear relationship was found between PEmax and T3 and T4 (r = -0.837 and r = -0.838, respectively, p less than 0.001). No relationship was found between maximal pressures and TSH. Finally, a significant linear relationship was found between PImax and PEmax (r = 0.872, p less than 0.001). Our results confirm that in thyrotoxicosis respiratory muscle weakness occurs that affects both inspiratory and expiratory muscles.(ABSTRACT TRUNCATED AT 250 WORDS)