title: Serum levels of insulin-like growth factor (IGF)-I and IGF binding protein (IGFBP)-1 to -6 and their relationship to bone metabolism in osteoporosis patients.
abstract: BACKGROUND: Insulin-like growth factor (IGF) system components are important regulators of bone formation. Alterations of individual IGF system components have been described in osteoporosis (OP) patients; however, no study has addressed changes in free IGF-I and in all six IGF binding proteins (IGFBPs). METHODS: A cross-sectional study was performed in 45 OP patients and 100 healthy matched controls. Serum levels of free and total insulin-like growth factor I (IGF-I), IGFBP-1 through -6, intact parathyroid hormone (PTH), 25-OH-vitamin D(3) (25OHD(3)), 1,25-(OH)(2)-vitamin D(3) (1,25-(OH)(2)D(3)), osteocalcin (OSC), bone alkaline phosphatase (B-ALP), and carboxyterminal propeptide of type-I procollagen (PICP) were measured with specific assays. Bone mineral density (BMD) of the lumbar spine was determined by dual-energy X-ray absorptiometry (DEXA). RESULTS: Compared with age- and sex-matched control subjects, OP patients showed a 73% decrease in free IGF-I, a 29% decrease in total IGF-I, a 10% decrease in IGFBP-3, and a 52% decrease in IGFBP-5 levels; they had higher levels of IGFBP-1 (4.1-fold), IGFBP-2 (1.8-fold), IGFBP-4 (1.3-fold), and IGFBP-6 (2.1-fold). Alterations in IGF system components were most evident in 13 OP patients with vertebral fractures in the past 4 years compared to patients without fractures. In OP patients with fractures, the ratio between IGFBP-4 and IGFBP-5 was increased whereas levels of OSC were decreased. CONCLUSIONS: Our data provide strong indirect evidence for a functional connection between circulating IGF system components and bone metabolism and the susceptibility to fractures in OP patients.
authors.affiliation: Abt. Innere Medizin, Krankenhaus der Paul-Gerhardt-Stiftung, Postfach 10 02 52, D-06872, Lutherstadt Wittenberg, Germany
authors.forename: Peter M.
authors.initials: PM
authors.lastname: Jehle
authors.forename: Klaus
authors.initials: K
authors.lastname: Schulten
authors.forename: Walter
authors.initials: W
authors.lastname: Schulz
authors.forename: Daniela R.
authors.initials: DR
authors.lastname: Jehle
authors.forename: Sylvia
authors.initials: S
authors.lastname: Stracke
authors.forename: Burkhard
authors.initials: B
authors.lastname: Manfras
authors.forename: Bernhard O.
authors.initials: BO
authors.lastname: Boehm
authors.forename: David J.
authors.initials: DJ
authors.lastname: Baylink
authors.forename: Subburaman
authors.initials: S
authors.lastname: Mohan