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Hypothyroidism- Need & Importance of Cardiopulmonary Rehabilitation

We know Hypothyroidism is a complex disease which is characterized by signs and symptoms that may have a significant negative impact on the quality of life and performance in the course of physical activity. These patients have lower physical activity levels, poor exercise tolerance which causes them to fatigue easily. Consequently, it leads to the deterioration of quality of life. These problems result from the insubstantial pulmonary reserve, limited cardiac reserve, reduced muscle strength or the increased tendency of muscle fatigue.
The exercise intolerance in hypothyroidism is multifactorial and is dependent on the functional limitations of the various system organs. Patients with hypothyroidism have been found to have decreased Cardio-respiratory fitness (VO2 max). Thyroid hormones maintain the functions of cardiovascular, respiratory systems and muscles during relaxation and during exercise. Decreased levels of thyroid hormones cause weakness in muscles of inspiration and expiration, alveolar hypoventilation and decreased hypoxic ventilator drive. It has been found that patients with hypothyroidism have decreased pulmonary functions which in turn lead to decrease oxygenation. Diminished pulmonary functions and capacities lead to reduced Cardio-respiratory fitness among patients with hypothyroidism. There occurs a reduction in contractile force of myocardium by changes in the structure of ATPase enzyme further affecting the pumping function of the heart and cardiac output which is a dominant factor in evaluating the level of Cardio-respiratory fitness.
There are increased incident of atherosclerotic lesions and cardiovascular events in subjects with hypothyroidism due to the increase in the concentration of total cholesterol, LDL and triglycerides and decrease in HDL levels. Total cholesterol and LDL levels are found to be raised due to decreased LDL receptors activity resulting in the reduced breakdown of LDL and IDL. Moreover reduction in Lipoprotein lipase activity is also found in clinical hypothyroidism which results in reduced clearance of triglycerides rich lipoproteins.
It is observed that there are variations in HR & BP response during exercise & recovery. The slow recovery in heart rate and decreased chronotropic response in subclinical hypothyroidism suggests that alteration in cardiac contractility, myocardial oxygen consumption, cardiac output, BP and systemic vascular resistance, negative association of HR recovery and Chronotropic response with TSH may suggest the abnormal TSH concentration may be noval cardiac risk factors.
Regular aerobic training has been found to improve the flow-mediated endothelium-dependent arterial dilation and change the lipid profile and inflammation in subclinical hypothyroidism. 12-week medium impact exercises have been found to be effective to increase cardio-respiratory fitness and health-related quality of life in subclinical hypothyroidism.
Researchers suggest that breathing training has a positive impact on the improvement of respiratory muscle functions & cardiac functions.

Dr. Sonia Pawaria
Assistant Professor, Faculty of Physiotherapy

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