Serum 25(OH)-Vitamin-D3 measurements.
25(OH)-Vitamin-D3 (=25(OH)VitD3) was measured in serum from baseline visits at the Dept. of Paediatrics and Adolescent Medicine of the Friedrich-Alexander Universität Erlangen-Nürnberg (Erlangen, Germany). Thereby LC-MS/MS MassChrom Kit from Chromosystems was used according to the manufacturers protocol.