Fig. 1

Association between insulin-like growth factor (IGF) levels and terminal duct lobular unit (TDLU) count among women with benign breast disease stratified by mammographic density. The association between levels of IGF proteins including IGF-I, IGF binding protein-3 (IGFBP-3) and the IGF-I:IGFBP-3 molar ratio, and TDLU count (modeled continuously) stratified by mammographic density are shown for a premenopausal women adjusted for age at biopsy, body mass index (BMI), age at first birth and percent fat on the tissue slide; and b postmenopausal women adjusted for age at biopsy, BMI, age at first birth and percent fat on the tissue slide. Analysis of IGFBP-3 and the molar ratio, but not IGF-I, in postmenopausal women was further adjusted for age at menarche, with the exception of the stratum for the highest tertile of mammographic density. Relative risk (RR) and 95 % confidence intervals (CI) were estimated using zero-inflated Poisson regression analysis, the outcome for the analysis was TDLU count (modeled continuously) and the independent variable was tertile of IGF-measure. These analyses were stratified by tertile of percent volumetric mammographic density; density tertiles were as follows: premenopausal: T1, <30.5 %; T2, 30.5 to <53 %; T3 ≥ 53.3 % and postmenopausal: T1, <22 %; T2, 22 to <33.3 %; T3, ≥33.3 %. P-int = P value for interaction