Serum free IGF-I, total IGF-I, IGFBP-1 and IGFBP-3 levels in an elderly population: relation to age and sex steroid levels

Clin Endocrinol (Oxf). 1998 Apr;48(4):471-8. doi: 10.1046/j.1365-2265.1998.00300.x.


Background: 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.

Measurements: 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.

Results: 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.

Conclusions: 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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Age Factors
  • Aged
  • Aged, 80 and over
  • Cross-Sectional Studies
  • Female
  • Gonadal Steroid Hormones / blood*
  • Humans
  • Insulin-Like Growth Factor Binding Protein 1 / blood
  • Insulin-Like Growth Factor Binding Protein 3 / blood
  • Insulin-Like Growth Factor Binding Proteins / blood*
  • Insulin-Like Growth Factor I / metabolism*
  • Male
  • Middle Aged


  • Gonadal Steroid Hormones
  • Insulin-Like Growth Factor Binding Protein 1
  • Insulin-Like Growth Factor Binding Protein 3
  • Insulin-Like Growth Factor Binding Proteins
  • Insulin-Like Growth Factor I