Sawin C T, Geller A, Kaplan M M, Bacharach P, Wilson P W, Hershman J M
Medical Services, Boston (Mass) Veterans Affairs Medical Center.
Arch Intern Med. 1991 Jan;151(1):165-8.
We studied a large population (n = 2575) of unselected ambulatory persons older than 60 years to determine the prevalence of a low serum thyroid-stimulating hormone (TSH) level, ie, of less than 0.1 mU/L using a sensitive assay, a level suggestive of hyperthyroidism in younger adults. One hundred one persons (3.9%) had a low serum TSH level. About half of them (51/101) were taking thyroid hormone. Of the remainder, 44 were not hyperthyroid did not become so during up to 4 years of follow-up. Forty-one of the 44 euthyroid persons had a serum thyroxine level of less than 129 nmol/L; repeated testing showed a serum TSH level of more than 0.1 mU/L in the three euthyroid persons with a serum thyroxine level of more than 129 nmol/L. Only six were hyperthyroid or became so during the follow-up period; all had a serum thyroxine level of more than 129 nmol/L. Routine clinical examination was not a sensitive indicator of hyperthyroidism and did not permit discrimination from euthyroidism. A low value of serum TSH alone, while it had high sensitivity and specificity for hyperthyroidism, had a low positive predictive value (12%) for this diagnosis; addition of the thyroxine assay raised the predictive value fivefold to 67%. A low value of serum TSH is far more common in older persons than is hyperthyroidism. Low values in euthyroid persons are accompanied by a clearly normal serum T4 concentration (less than 129 nmol/L) or by a serum TSH level of more than 0.1 mU/L on repeated testing. We recommend measurement of the serum TSH thyroid concentration, using a sensitive assay, as the initial step in testing any older person for possible hyperthyroidism. Measurement of the serum T4 concentration or the free T4 index on the same sample would be needed only in the approximately 2% with a serum TSH level of less than 0.1 mU/L; alternatively, the TSH assay in these could be repeated at a later time.
我们研究了一大群（n = 2575）60岁以上未经过挑选的门诊患者，以确定血清促甲状腺激素（TSH）水平低（即使用敏感检测法低于0.1 mU/L，这一水平在年轻成年人中提示甲状腺功能亢进）的患病率。101人（3.9%）血清TSH水平低。其中约一半（51/101）正在服用甲状腺激素。其余人中，44人并非甲状腺功能亢进，且在长达4年的随访期间也未出现甲状腺功能亢进。44名甲状腺功能正常的人中，41人的血清甲状腺素水平低于129 nmol/L；重复检测显示，血清甲状腺素水平高于129 nmol/L的3名甲状腺功能正常者的血清TSH水平高于0.1 mU/L。随访期间只有6人是甲状腺功能亢进或后来发展为甲状腺功能亢进；他们的血清甲状腺素水平均高于129 nmol/L。常规临床检查并非甲状腺功能亢进的敏感指标，无法将其与甲状腺功能正常区分开来。单独血清TSH值低虽然对甲状腺功能亢进具有高敏感性和特异性，但该诊断的阳性预测值较低（12%）；加上甲状腺素检测后，预测值提高了五倍，达到67%。血清TSH值低在老年人中比甲状腺功能亢进更为常见。甲状腺功能正常者TSH值低时，血清T4浓度明显正常（低于129 nmol/L），或重复检测时血清TSH水平高于0.1 mU/L。我们建议，对任何可能患有甲状腺功能亢进的老年人进行检测时，首先使用敏感检测法测量血清TSH甲状腺浓度。仅约2%血清TSH水平低于0.1 mU/L的人需要测量同一样本的血清T4浓度或游离T4指数；或者，也可以在之后对这些人重复进行TSH检测。
