Longitudinal changes in IGF1 and IGFBP3, and mammographic density among postmenopausal women
A partir de données portant sur 302 femmes ménopausées (âge: 50 à 74 ans), cette étude longitudinale évalue l'association entre l'évolution des niveaux de concentration de l'hormone IGF-1 circulante et de la protéine IGFBP3 et la densité mammaire
A relation between the breast cancer risk factors, insulin-like growth factor-1 (IGF-1) and mammographic density, is biologically plausible, but results from cross-sectional epidemiologic studies have been mixed. Our objective was to examine the relation in a longitudinal manner, i.e., between the change in circulating IGF-1 concentrations and the change in mammographic measures over one year. Data from an exercise intervention trial conducted in 302 postmenopausal women aged 50 -74 years were used. Blood drawn at baseline and post-intervention was assessed for IGF-1 and its binding protein (IGFBP-3) by direct chemiluminscent immunoassay. Area and volumetric measurements of mammographic dense fibroglandular and nondense fatty tissue were made. Statistical analyses were based on multiple linear regression. Results: A one standard deviation (20.2 ng/mL) change in IGF-1 over 1 year was associated with small changes in percent dense area (mean: 0.8%; 95% confidence interval (CI): 0.1 - 1.4) and dense area (mean: 1.2 cm2; 95% CI: 0.2 - 2.1). Change in IGFBP-3 was also associated with percent and absolute dense area. Absolute and percent dense volume, and mammographic measures representing fatty tissue (nondense area and volume) were not associated with changes in IGF-1 and IGFBP-3. Longitudinal associations may be more detectable than cross-sectional associations due to the absence of confounding by invariant personal factors. Absolute and percent dense area, measures that are related to breast cancer risk, may be affected by IGF-1. Confirmation should be sought in further longitudinal studies in which larger changes in the IGF system are evoked.