Endogenous diurnal patterns of adrenal and gonadal hormones during a 24 hour constant routine after simulated shiftwork

Abstract Context Night shiftwork causes circadian misalignment, predicts the development of metabolic diseases, and complicates the interpretation of hormone measurements. Objective To investigate endogenous circadian rhythms, dissociated from behavioral and environmental confounds, in adrenal and gonadal steroids after simulated shiftwork. Methods Fourteen healthy adults (ages 25.8 ± 3.2 years) were randomized to 3 days of night or day (control) shiftwork followed by a constant routine protocol designed to experimentally unveil rhythms driven endogenously by the central circadian pacemaker. Blood was sampled every 3 hours for 24-hours during the constant routine to concurrently obtain sixteen Δ4 steroid profiles by mass-spectrometry. Cosinor analyses of these profiles provided mesor (mean abundance), amplitude (oscillation magnitude) and acrophase (peak timing). Results Night shiftwork marginally increased cortisol by 1 μg/dL (p = 0.039), and inactive/weak derivatives cortisone (p = 0.003) and 18-hydroxycortisol (p < 0.001), but did not alter the mesor of potent androgens testosterone and 11-ketotestosterone. Adrenal-derived steroids, including 11-ketotestosterone (p < 0.01), showed robust circadian rhythmicity after either day or night shiftwork. In contrast, testosterone and progesterone showed no circadian pattern after both shiftwork conditions. Night shiftwork did not alter the amplitude or acrophase of any of the steroid profiles. Conclusions Experimental circadian misalignment had minimal effects on steroidogenesis. Adrenal steroids, but not gonadal hormones, showed endogenous circadian regulation robust to prior shift schedule. This dichotomy may predispose night shiftworkers to metabolic ill-health. Furthermore, adrenal steroids including cortisol and the main adrenal androgen 11-ketostosterone should always be evaluated during the biological morning whereas assessment of gonadal steroids, particularly testosterone, is dependent on the shiftwork schedule.