IGF1 and X-linked dominant hypophosphatemic rickets: Additionally, when compared with the control, SS levels were reduced in the GLY and PRO groups (p < 0.001) but increased in the HYP group (p < 0.001), whereas IGF-1 levels were significantly higher in the GLY (p < 0.001) and HYP (p < 0.001) groups (Figure 1).