Fig. 3.

Endogenous circadian rhythm in plasma aldosterone during relaxed wakefulness while supine. Plasma aldosterone measured during standardized relaxed wakefulness while supine immediately after scheduled awakenings displays a large and significant endogenous circadian rhythm, with aldosterone doubling across the usual sleep period and peaking in the biological morning at ~8 AM (n = 16, P < 0.001 using mixed-model cosinor analyses). The circadian model is plotted from the cosinor analyses. Raw observed values were binned by circadian phase within subject and then averaged within group and are plotted as means ± SE.