FIGURE 1.

Development of peripheral indicators of iron status. Hemoglobin (left), ferritin (center), and transferrin (right) were significantly associated with age throughout the first 2 decades of life (A). Sex differences in developmental trajectories emerged during adolescence such that females tended to decline in iron status (red lines) relative to males (blue lines). Rescaling chronological age to reflect years from self-reported menarche revealed that developmental trajectories changed after menarche for females (B). Solid lines reflect spline fits from generalized additive models; shaded areas reflect 95% CIs of the fit. Density plots on right and top edges depict the distribution of the plotted variables. Horizontal bars below the x-axis depict the significance of age-related change (derivatives of the fitted spline function). The outline of the bar indicates age-related change for males (blue) or females (red). The filled portion of the bar indicates windows of significant change; the saturation of the fill represents the magnitude of change (derivative magnitude).