The serum DKK1 concentration in OI children was negatively correlated with the ALP concentration (r = − 0.304, P < 0.05) (Fig. 4a) and positively correlated with serum calcium concentration (r = 0.257, P < 0.05) (Fig. 4d) and negatively correlated with PTH concentration (r = − 0.269, P < 0.05) (Fig. 4e). The gene discussed is DKK1; the disease is osteogenesis imperfecta.