Burroughs V, Shenkman L
Am J Med Sci. 1982 Jan-Feb;283(1):8-17. doi: 10.1097/00000441-198201000-00002.
Thyroid dysfunction is common in older individuals, yet the diagnosis is often complicated by atypical clinical presentations and difficulty in interpretation of laboratory tests. An understanding of the alterations in thyroid function occurring normally as a consequence of the aging process is necessary for correct laboratory diagnosis of thyroid dysfunction in the elderly. There are subtle alterations in hypothalamic and pituitary function but normal feedback control of TSH secretion persists. In the thyroid itself, morphologic changes develop with age, but have little impact on thyroid hormone economy. Thyroidal secretion of thyroxine decreases, but parallels the decrease in thyroxine degradation rate, resulting in unaltered plasma thyroxine levels. Decreased peripheral conversion of thyroxine to triiodothyronine causes a fall in triiodothyronine concentrations. Nonthyroidal illnesses in the elderly may perturb the laboratory assessment of thyroid function by producing isolated high or low thyroxine levels in euthyroid individuals.
甲状腺功能障碍在老年人中很常见，但非典型临床表现和实验室检查结果解读困难常常使诊断变得复杂。了解衰老过程中甲状腺功能正常发生的变化，对于正确诊断老年人的甲状腺功能障碍至关重要。下丘脑和垂体功能存在细微变化，但促甲状腺激素（TSH）分泌的正常反馈控制仍然存在。甲状腺本身会随着年龄增长出现形态学变化，但对甲状腺激素代谢影响不大。甲状腺素的甲状腺分泌减少，但与甲状腺素降解率的降低相平行，导致血浆甲状腺素水平保持不变。甲状腺素向三碘甲状腺原氨酸的外周转化减少导致三碘甲状腺原氨酸浓度下降。老年人的非甲状腺疾病可能通过使甲状腺功能正常的个体出现孤立的高甲状腺素水平或低甲状腺素水平，干扰甲状腺功能的实验室评估。
