Serum levels of insulin-like growth factor-I are related to age and not to body composition in healthy women and men

J Gerontol A Biol Sci Med Sci. 1998 May;53(3):M176-82. doi: 10.1093/gerona/53a.3.m176.


Background: Aging is accompanied by decreased bone and lean body mass, increased fat mass, and reduced growth hormone (GH) axis function, reflected in diminished levels of insulin-like growth factor-I (IGF-I). Similar changes in body composition occur in nonelderly, GH-deficient adults and are reversible with GH administration, suggesting that diminished GH/IGF-I axis activity may contribute to such age-related changes. To determine the precise pattern of IGF-I decline with age, and to test the hypothesis that this decline is related to concomitant changes in body composition and bone metabolism independent of age, we conducted a cross-sectional survey in 351 healthy participants in the Baltimore Longitudinal Study of Aging.

Methods: We evaluated relationships among IGF-I, age, and total and regional adiposity, as assessed by body mass index (BMI) and waist-to-hip ratio (WHR); lean body mass, as estimated from urinary creatinine excretion (Crex/ht); bone mineral density (BMD), as assessed by single and dual photon absorptiometry scanning; and circulating levels of parathyroid hormone (PTH), 1,25-(OH)2 D3, 25-OHD, and osteocalcin.

Results: Serum IGF-I levels declined with age (p < .0001) in both men (r = -.51) and women (r = -.67). In men, the decline was linear, whereas IGF-I levels decreased faster in women < 45 years of age than in older women (p < .01) or in men (p < .001). IGF-I was inversely related to BMI (p < .005), WHR (p < .001), and PTH (p < .01) in women. IGF-I was positively related to BMD of the hip and radius in both genders (p < .0003) and to Crex/ht (p < .0005) and osteocalcin (p < .0001) in men. With increasing age, Crex/ht and BMD decreased (p < .0001) and WHR, PTH, and osteocalcin increased (p < .005) in both genders, whereas BMI increased only in women (p < .005). After adjustment for age, IGF-I was not significantly related to BMI, WHR, Crex/ht, or BMD in either gender. IGF-I was positively related to 1,25-(OH)2 D3 (p < .01) independently of age in women.

Conclusions: Advancing age, rather than declining serum levels of IGF-I, appears to be a major determinant of life-time changes in body composition and BMD in women and men.

MeSH terms

  • Adult
  • Age Factors
  • Aged
  • Aged, 80 and over
  • Aging / blood*
  • Body Composition / physiology*
  • Body Mass Index
  • Bone Density
  • Calcifediol / blood
  • Calcitriol / blood
  • Female
  • Human Growth Hormone / blood
  • Humans
  • Insulin-Like Growth Factor I / metabolism*
  • Male
  • Middle Aged
  • Osteocalcin / blood
  • Parathyroid Hormone / blood
  • Reference Values
  • Regression Analysis
  • Sex Characteristics


  • Parathyroid Hormone
  • Osteocalcin
  • Human Growth Hormone
  • Insulin-Like Growth Factor I
  • Calcitriol
  • Calcifediol