Hypothyroidism and exercise tolerance

What is it about?

Purpose: This systematic review describes the state of the art of the impact of hypothyroidism on exercise tolerance and physical performance capacity in untreated and treated patients with hypothyroidism. Method: A systematic computer-aided search was conducted using biomedical databases. Relevant studies in English, German, and Dutch, published from the earliest date of each database up to December 2012, were identified. Results: Out of 116 studies, a total of 38 studies with 1,379 patients fulfilled the inclusion criteria. These studies emphasize the multifactorial causes of exercise intolerance in untreated patients by the impact of limitations in different functional systems, with cardiovascular, cardiopulmonary, musculoskeletal, neuromuscular, and cellular metabolic systems acting in concert. Moreover, the studies affirm that exercise intolerance in patients is not always reversible during adequate hormone replacement therapy. As a consequence, despite a defined euthyroid status, there remains a significant group of treated patients with persistent complaints related to exercise intolerance who are suffering from limitations in daily and sport activities, as well as an impaired quality of life. An explanation for this phenomenon is lacking. Only 2 studies investigated the effects of a physical training program, and they showed inconsistent effects on the performance capacity in untreated patients with subclinical hypothyroidism. Conclusions: A limited body of knowledge exists concerning exercise tolerance in treated patients with hypothyroidism, and there is an insufficient amount of quantitative studies on the effects of a physical training program. To enhance exercise and sports participation for this specific group, more research in this forgotten area is warranted.

Featured Image

Why is it important?

This review shows that primary hypothyroidism can lead to significant adverse effects on physical well-being in both untreated and treated patients, making them more intolerant for physical exercise than healthy participants. This intolerance leads to physical inactivity, physical deconditioning (muscle atrophy and weakness, fatigue, obesity), and increased risk for cardiovascular events. However, one may expect that regular physical activity contributes to an improvement of the quality of life in patients, as beneficial physiological and psychological adaptations to such a lifestyle make daily life activities more tolerable. According to this review, there exist inconsistent data concerning the effects of physical training programs in patients with primary hypothyroidism, which currently does not contribute to novel practical knowledge on secondary prevention. Therefore, future studies are warranted with a focus on implementation of an active lifestyle and prevention of deconditioning through effective exercise programs for this group of patients. Implications for daily practice will be that sports physicians, endocrinologists, and coaches will be consulted more by patients with a desire to exercise on a regular basis or to participate in sport activities.