Anna Tiihonen Möller, Torbjörn Bäckström, Hans Peter Söndergaard, Mark M Kushnir, Jonas Bergquist and Lotti Helström
Rationale: The diurnal variations of cortisol and of other upstream glucocorticoid steroids have been well described. However, diurnal variations of other steroids in the steroid synthesis pathways have not been fully addressed in the literature. Objective: To explore possible diurnal variations of several endogenous steroids. Methods: Blood samples were taken every fourth hour during 24 hours in 10 healthy drug naïve pre-menopausal women in the follicular phase of the menstrual cycle. Using the LC-MS/MS technique, serum was analyzed for concentrations of glucocorticoids (cortisol, cortisone, 11-deoxycortisol), androgens (androstenedione, testosterone, DHEA), pregnenes (pregnenolone, 17OH-pregnenolone), progestins (progesterone, 17OH-progesterone), and estrogens (estrone, estradiol). The concentration of the anesthetic steroid allopregnanolone was analyzed using the radioimmunoassay (RIA) technique. The blood samples were divided into six time intervals; 02:01-06:00, 06:01-10:00, 10:01-14:00, 14:01-18:00, 18:01-22:00, and 22:01-02:00. Each steroid was tested for possible diurnal variation using repeated measures ANOVA for within-subject variation. Results: All steroids except the estrogens exhibited a significant diurnal variation (p<0.05). Apart from allopregnanolone, all the steroids peaked in concentration at 08:00 (e.g., just after awakening). Allopregnanolone had a flatter curve, its highest concentrations occurring throughout the day and its peak concentrations at about 12:00. Conclusions: The present study suggests that when assessing concentrations of steroids in the glucocorticoid group and those in the pregnene, androgen, and progestine groups, as well as allopregnanolone, it might be necessary to accounted for a diurnal variation. However, a possible interaction between menstrual-cycle phase and the hypothalamus-pituitary-adrenal (HPA) axis and the diurnal variations of the steroids should be confirmed by future studies.