Fig. 9
Numerical simulations of 25(OH)D and its metabolites with age. The predicted concentrations of (a) extracellular 25(OH)D, (b) extracellular 1,25(OH)2D, (c) intracellular 25(OH)D, (d) intracellular 1,25(OH)2D and (e) the VDR:1,25(OH)2D complex with age, from solving Eqs. (3)–(23) with baseline parameters given in Tables 1, 2 and 3 and age functions given in Figs. 2, 3, 4 and 5. The production rates \(D^{0}\) and \(D^{1}\) to attain a concentration of 50 nmol/L (red line) and 75 nmol/L (blue line) 25(OH)D at age 20 years are \(D^{0}=3.2\), 4.8 and \(D^{1}=0.35\), 0.5 nmol/L day−1, respectively.
