Differential life cycle expression of genes encoding qualified and proposed kidney biomarkers. Genes encoding qualified renal biomarkers Kim-1, Clu, Tff3, Lcn2, Spp1, and proposed renal biomarker Fetuin A show sex differences in expression from 2- to 600-fold in the kidney. Relative fold changes (microarray data) are plotted; error bars represent SEM, n = 4 or 5. Females and males are indicated by dashed and solid lines, respectively. Averaged expression levels (normalized fluorescence intensities) across all age groups and in both sexes are reported for each gene and have been scaled to equal 1 in the plots.