Insulin-like growth factor-1, growth hormone, and daily cycling estrogen are associated with mammographic density in premenopausal women

Abstract

Background: Mammographic density represents epithelial and stromal proliferation, while Insulin-like growth factor (IGF)-1, IGF-binding protein (IGFBP)-3, growth hormone (GH) and estrogen, may influence cellular proliferation. However, whether these growth factors independently, or in combination with estrogen, influence mammographic density in premenopausal women remains unclear. Material and methods: Growth factors were assessed in 202 ovulating premenopausal women participating in the Energy Balance and Breast cancer Aspects (EBBA)-I study. Estrogen was assessed in serum, and daily in saliva, throughout a menstrual cycle. Computer-assisted mammographic density (Madena) was obtained from digitized mammograms (days 7-12 of the menstrual cycle). Associations between growth factors, estrogen and percent mammographic density, were studied in regression models. Results: Women with a mean age of 30.7 years had a mean percent mammographic density of 29.8%. Among women in the strata (above median split) of IGF-1 (>25 nmol/l) or GH (>0.80 mlU/l), we observed that an increase in salivary 17β–estradiol, was associated with a higher odds for having higher percent mammographic density (>28.5 %). The odds ratios (ORs) per standard deviation increase of 17β-estradiol, were 1.81 (95% confidence interval [CI] 1.08-3.03) in the high IGF-1 stratum, and 2.08 (95% CI 1.10-3.94) in the high GH stratum. Furthermore, women in this strata of growth factors (above median) who had an overall average 17β–estradiol above median (>16.8 pmol/l), had higher ORs for having higher percent mammographic density (>28.5%): IGF-1 4.13 (95% CI 1.33-12.83), and GH 4.17 (95% CI 1.41-12.28). Conclusion: Growth factors, in combination with cycling estrogen, were associated with percent mammographic density, of potential clinical relevance.