Harman S M, Wehmann R E, Blackman M R
J Clin Endocrinol Metab. 1984 Feb;58(2):320-6. doi: 10.1210/jcem-58-2-320.
In order to assess the effects of aging, as distinct from those of thyroid disease or extrathyroidal illness, on certain indices of thyroid function, we studied 74 healthy, ambulatory men recruited from the Baltimore Longitudinal Study on Aging. We determined basal serum values of T4, T3, rT3, thyroxine-binding globulin (TBG), and T3 resin uptake (T3RU) and calculated the free T4 index (FT4I = T4 X T3RU/100), free T3 index (FT3I = T3 X T3RU/100), and T4/TBG ratio for each subject. We used an ultrasensitive RIA to measure variations in basal concentrations of TSH within the normal range. We then infused TRH at a constant rate (0.4 microgram/min iv) for 240 min into 63 of the same men; serum samples, collected at 15-min intervals during the infusion, were analyzed for TSH by routine RIA. Subjects were divided into 3 groups according to age; A (n = 26, mean age = 39.4), B (n = 23, mean age = 60.0), and C (n = 25, mean age = 79.6). Analysis of variance with Duncan's multiple range test and regression analysis were used to evaluate data. There was no significant (P greater than 0.05) variation with age of basal serum values of T4, TBG, or T3RU. Comparison of groups A and C showed significant decreases of mean values of serum T3 (-11%, P less than 0.05), FT3I (-13%, P = 0.02), FT4I (-11%, P less than 0.01), and T4/TBG ratio (-12%, P less than 0.01) and an increase in serum TSH (+38%, P less than 0.05). For these variables, the mean values for group B were intermediate between, but not significantly different from, those of A and C. Regression analysis showed significant correlations of age with T3, FT3I, FT4I, T4/TBG, and TSH at P levels similar to those obtained by Duncan's test. No elderly individual exhibited a baseline elevation of TSH (greater than 7 microU/ml) or depression of T4 (less than 5 micrograms/dl), suggesting that primary hypothyroidism was not present in our old group. The basal TSH concentration did not correlate significantly with any index of thyroid function except with FT3I in group C (r = -0.43, P less than 0.05). In all age groups the TSH responses to TRH exhibited a biphasic pattern with early and late peaks.(ABSTRACT TRUNCATED AT 400 WORDS)
为了评估衰老（与甲状腺疾病或甲状腺外疾病相区别）对某些甲状腺功能指标的影响，我们研究了从巴尔的摩纵向衰老研究中招募的74名健康、可走动的男性。我们测定了T4、T3、反T3、甲状腺素结合球蛋白（TBG）的基础血清值以及T3树脂摄取率（T3RU），并计算了每个受试者的游离T4指数（FT4I = T4×T3RU/100）、游离T3指数（FT3I = T3×T3RU/100）和T4/TBG比值。我们使用超灵敏放射免疫分析法来测量正常范围内基础促甲状腺激素（TSH）浓度的变化。然后，我们以恒定速率（0.4微克/分钟静脉注射）向其中63名相同男性输注促甲状腺激素释放激素（TRH）240分钟；在输注过程中每隔15分钟采集血清样本，通过常规放射免疫分析法分析TSH。受试者根据年龄分为3组；A组（n = 26，平均年龄 = 39.4岁）、B组（n = 23，平均年龄 = 60.0岁）和C组（n = 25，平均年龄 = 79.6岁）。采用方差分析及邓肯多重极差检验和回归分析来评估数据。T4、TBG或T3RU的基础血清值随年龄无显著（P＞0.05）变化。A组和C组比较显示，血清T3平均值显著降低（-11%，P＜0.05）、FT3I（-13%，P = 0.02）、FT4I（-11%，P＜0.01）和T4/TBG比值（-12%，P＜0.01），血清TSH升高（+38%，P＜0.05）。对于这些变量，B组的平均值介于A组和C组之间，但与它们无显著差异。回归分析显示，年龄与T3、FT3I、FT4I、T4/TBG和TSH在P水平上有显著相关性，与邓肯检验获得的结果相似。没有老年个体表现出TSH基线升高（＞7微单位/毫升）或T4降低（＜5微克/分升），这表明我们的老年组不存在原发性甲状腺功能减退。基础TSH浓度除与C组的FT3I显著相关（r = -0.43，P＜0.05）外，与任何甲状腺功能指标均无显著相关性。在所有年龄组中，TSH对TRH的反应呈现双相模式，有早期和晚期峰值。（摘要截断于400字）
