| مستخلص: |
Thyroid hormones have vital roles in development, growth and energy metabolism. Within the past two decades, disturbances in thyroid hormone action have been implicated in ageing and the development of age-related diseases. This Review will consider results from biomedical studies that have identified the importance of precise temporospatial regulation of thyroid hormone action for local tissue maintenance and repair. Age-related disturbances in the maintenance of tissue homeostasis are thought to be important drivers of age-related disease. In most iodine-proficient human populations without thyroid disease, the mean, median and 97.5 centile for circulating concentrations of thyroid-stimulating hormone are progressively higher in adults over 80 years of age compared with middle-aged (50–59 years) and younger (20–29 years) adults. This trend has been shown to extend into advanced ages (over 100 years). Here, potential causes and consequences of the altered thyroid status observed in old age and its association with longevity will be discussed. In about 5–20% of adults at least 65 years of age, thyroid-stimulating hormone concentrations are elevated but circulating concentrations of thyroid hormone are within the population reference range, a condition referred to as subclinical hypothyroidism. Results from randomized clinical trials that have tested the clinical benefit of thyroid hormone replacement therapy in older adults with mild subclinical hypothyroidism will be discussed, as well as the implications of these findings for screening and treatment of subclinical hypothyroidism in older adults. Thyroid hormones have key functions throughout the body. However, thyroid function declines with age and thyroid diseases increase in prevalence. This Review outlines our current knowledge about how thyroid function changes with age and the implications for patient care. Key points: In line with the emerging role of thyroid hormone action in tissue maintenance and repair, studying local control of thyroid hormone in ageing is an area urgently in need of research. The mechanisms contributing to altered thyroid status in old age are probably heterogeneous and comprise selective survival, transient age-related changes and persistent age-related changes. Increased circulating levels of thyroid-stimulating hormone and/or reduced circulating levels of thyroid hormone is a heritable phenotype associated with exceptional longevity. Subclinical hypothyroidism is a frequent diagnosis among older adults; in randomized clinical trials, levothyroxine therapy provided no apparent clinical benefits in older adults with mild subclinical hypothyroidism. Older adults form a heterogeneous group, so future research should explore strategies for safe screening, initiation, continuation and/or discontinuation of treatment of subclinical hypothyroidism in specific subgroups of older adults. [ABSTRACT FROM AUTHOR] |
