Male internal medicine residents (n = 8, 30 to 47 years of age) agreed to collect two 24-hour urine samples (beginning at 8 am), one during a weekend while off duty and one while on regular night-shift duty at the General Hospital of Vienna. The sequence of the two urine collections was arbitrary. Steroid excretion rates were compared with those obtained in a group of 16 healthy, normal-weight men of similar age.
Urine samples were processed as reported previously (5). Quantification of excreted steroids with standardization for each steroid (5) was done by gas chromatography-mass spectrometry in selected-ion–monitoring mode and after electric fragmentation using a Hewlett Packard 5973 mass selective detector (Palo Alto, California) equipped with a 25 m chemical-bound 5% fused-silica column. Dihydrotestosterone and progesterone were used as internal standards to assess the quality of the respective derivatization. M+ or M+-90 were used as tracing ions. The sensitivity was 1 pg per injection.