Figure 3. Schematic depiction of longitudinal changes in calcium, phosphorus, and calciotropic hormone levels during lactation and post-weaning skeletal recovery in women. Normal adult values are indicated by the shaded areas. PTH does not decline in women with low calcium or high phytate intakes and may even rise above normal. Calcidiol (25OHD) values are not depicted; most longitudinal studies indicate that the levels are unchanged by lactation but may vary due to seasonal variation in sunlight exposure and changes in vitamin D intake. PTHrP and prolactin surge with each suckling episode, and this is represented by upward spikes. FGF23 values cannot be plotted due to lack of data. Very limited data suggest that calcitriol and PTH may increase during post-weaning, and the lines are dashed to reflect the uncertainty. Reproduced with permission from (1).