Janssen J A, Stolk R P, Pols H A, Grobbee D E, de Jong F H, Lamberts S W
Department of Internal Medicine III, Erasmus University, Rotterdam, The Netherlands.
Clin Endocrinol (Oxf). 1998 Apr;48(4):471-8. doi: 10.1046/j.1365-2265.1998.00300.x.
Most previous studies concerning the relationship between IGF-I and age used assays measuring total IGF-I. Although free IGF-I is considered of greater biological relevance, little is known about its relationship with sex steroids levels in elderly healthy subjects.
In a cross-sectional study of 218 healthy people (103 men, 115 women) aged 55-80 years we measured serum total and free IGF-I, IGFBP-1 and IGFBP3 levels and sex steroids. Free androgen index and free oestradiol index were used as an indicator for free oestradiol and free testosterone levels, respectively.
Free IGF-I levels did not decline with age in the whole study population. Free IGF-I levels even increased in individuals above 70 years of age in comparison to those aged between 55 and 70 years (mean +/- SE 0.106 +/- 0.007 nmol/l vs. 0.086 +/- 0.004 nmol/l, P = 0.009). Total IGF-I and IGFBP-3 decreased with age (r = -0.20, P = 0.005 and r = -0.24, P = 0.001, respectively). Total IGF-I levels were positively related with free oestrogen index in both sexes. Free IGF-I did not relate to free oestrogen or androgen index. In women only, free IGF-I was related positively with DHEAS while IGFBP-1 was inversely correlated with DHEAS.
Free IGF-I levels do not decrease with age and are even higher in individuals above 70 years. There was no relationship between free IGF-I and free androgen or oestrogen index in either gender. We hypothesize that higher free IGF-I levels in older persons may be the consequence of selective survival in the cohort: subjects with high free IGF-I levels may live longer. The absence of a relationship between free IGF-I levels and free androgen and oestrogen indices suggests that there is no direct interaction between the biological activity of circulating IGF-I levels and sex hormone production in a healthy ageing population.
以往大多数关于胰岛素样生长因子-I（IGF-I）与年龄关系的研究使用的是测量总IGF-I的检测方法。尽管游离IGF-I被认为具有更大的生物学相关性，但对于其在老年健康受试者中与性激素水平的关系却知之甚少。
在一项对218名年龄在55至80岁的健康人（103名男性，115名女性）的横断面研究中，我们测量了血清总IGF-I和游离IGF-I、胰岛素样生长因子结合蛋白-1（IGFBP-1）和胰岛素样生长因子结合蛋白-3（IGFBP3）水平以及性激素。游离雄激素指数和游离雌二醇指数分别用作游离雌二醇和游离睾酮水平的指标。
在整个研究人群中，游离IGF-I水平并未随年龄下降。与55至70岁的个体相比，70岁以上个体的游离IGF-I水平甚至有所升高（均值±标准误 0.106±0.007 nmol/L 对 0.086±0.004 nmol/L，P = 0.009）。总IGF-I和IGFBP-3随年龄下降（r = -0.20，P = 0.005和r = -0.24，P = 0.001）。总IGF-I水平在两性中均与游离雌激素指数呈正相关。游离IGF-I与游离雌激素或雄激素指数无关。仅在女性中，游离IGF-I与硫酸脱氢表雄酮（DHEAS）呈正相关，而IGFBP-1与DHEAS呈负相关。
游离IGF-I水平不会随年龄降低，在70岁以上个体中甚至更高。在任何性别中，游离IGF-I与游离雄激素或雌激素指数之间均无关联。我们推测，老年人中较高的游离IGF-I水平可能是该队列中选择性生存的结果：游离IGF-I水平高的个体可能寿命更长。游离IGF-I水平与游离雄激素和雌激素指数之间缺乏关联表明，在健康老龄化人群中，循环IGF-I水平的生物学活性与性激素产生之间不存在直接相互作用。
