*2.4. QC Samples*

To control the quality of the metabolic profile (fingerprint) measurement, a constant amount of the internal 17β-testosterone-D2 standard was added to each plasma and urine sample (Figure 8), and pooled QC samples were included in each measured acquisition. The RT (deviation up to 10%), peak area (deviation up to 10%) and MA (Δppm <3) were checked in each measured metabolomic profile.

**Figure 8.** Pooled urine QC sample, control chromatogram for internal standard and corresponding mass spectrum (experimental *m*/*z* = 291.22879, Δppm = 0.1).
