SERUM INSULIN-LIKE-GROWTH-FACTOR BINDING-PROTEIN (IGFBP)-4 AND IGFBP-5 LEVELS IN AGING AND AGE-ASSOCIATED DISEASES

Because impaired bone formation is a major contributor to the pathogen esis of senile (type II) osteoporosis, and because insulin-like growth factors (IGFs) have been shown to be important stimulators of bone fo rmation in vitro and in vivo, studies have been focused towards clarif ying the role of IGF system in the age-related impairment in bone form ation. To evaluate if changes in circulating and bone cell production of IGF binding protein (IGFBP)-4 and IGFBP-5 could contribute to age-r elated impairment in bone formation, the authors measured serum and sk eletal levels of IGFBP-5, and serum levels of IGFBP-4 during aging. Ci rculating levels of IGFBP-4 increased with age, whereas that of IGFBP- 5 declined with age. Serum IGFBP-4 and IGFBP-5 levels showed significa nt positive correlations with serum levels of parathyroid hormone (PTH ) and IGFs, respectively. In addition, skeletal content of IGFBP-5 dec lined with age. The age-related changes in IGFBP-4 and IGFBP-5 product ion could contribute, in part, to the decrease in osteoblast cell prol iferation and deficiency in bone formation.