Diurnal urinary excretion of cortisol and aldosterone in kidney graft recipients

In 13 supine kidney graft recipients in the late post-transplant period the circadian rhythms of urinary cortisol and aldosterone excretion were studied. An inversion of the circadian rhythm of urinary cortisol excretion was found, with acrophase occuring in the night time. Plasma cortisol level, measured in 6 h intervals, attained the maximal mean value at 24 h. Urinary aldosterone excretion in most of the patients demonstrated also an inversed circadian rhythm with acrophase occuring from 21 to 03 h. In 6 patients the 24 h urinary aldosterone excretion was above the upper limit for healthy persons. The peak plasma aldosterone level was found at 24 h; it greatly exceeded the upper limit of aldosterone level in healthy supine persons. In 5 out of 13 patients the plasma renin activity (PRA) was above the upper limit of normal for supine subjects. The maximal mean PRA level was found at 24 h. The study in kidney graft recipients has established an inversed circadian rhythm of urinary cortisol and aldosterone excretion, probably related to the immunosuppressive treatment and reduced kidney function.