Oasis max spe system plates

Blood samples were obtained from an antecubital vein in monovettes (Sarstedt, Germany) in the early morning before 8 am after an overnight fast and transferred within 1 h after sampling to the laboratory of the University Hospital Essen for analyses. Serum and plasma aliquots were stored at −80°C until testosterone and cortisol were determined by liquid-chromatography tandem mass spectrometry [LC-MS/MS; (23 (link), 24 (link))]. In brief, the stored sample aliquots, aliquots of calibrator and controls with a volume of 0.1 mL were combined with the internal standard mixture to monitor recovery. All samples were extracted using Oasis MAX SPE system Plates (Waters, Milford, MA, USA). LC-MS/MS was performed using a Waters Quattro Premier/Xe triple-quadrupole mass spectrometer connected to a Waters Acquity (Waters, Milford, MA, USA; Table 1 for details on assays).
To consider the biologically active fraction of testosterone and for reasons of comparability with previous studies, free testosterone (FT) levels were calculated according to Vermeulen et al. (25 (link)).

Blood samples were obtained from an antecubital vein in the early morning (6:30 to 8:00 am) after an overnight fast and transferred within one hour after sampling to the laboratory of the University Hospital Essen for analyses. Serum and plasma aliquots were stored at -80°C until steroid metabolome analysis by liquid-chromatography tandem mass spectrometry (LC-MS/MS) (24 (link), 25 (link)). In brief, for LC-MS/MS analysis, the stored sample aliquots the calibrator and controls aliquots were combined with the internal standard mixture to monitor recovery. All samples were extracted using Oasis MAX SPE system Plates (Waters, Milford, MA, USA). LC-MS/MS was performed using a Waters Quattro Premier/Xe triple-quadrupole mass spectrometer connected to a Waters Acquity (Waters, Milford, MA, USA; Table 1 for details on assays).