Uraemia and adrenocortical function in Nigerian subjects.

In assessing the pituitary-adrenal axis of uraemic Nigerians, we investigated the circadian rhythm of plasma cortisol secretion, the response to the overnight dexamethasone (1 mg) suppression test and the pattern of excretion of urinary free cortisol (UFC) in 10 uraemic subjects and nine non-uraemic controls. Basal (0800 h) plasma cortisol levels were similar in both uraemic (mean +/- s.e.m.; 224 +/- 36 nmol/l) and non-uraemic (218 +/- 47 nmol/l) subjects. The non-uraemic subjects demonstrated the normal late night (2300 h) reduction in cortisol levels but this was absent in uraemic subjects in whom the basal and late night values were similar. Post-dexamethasone (0800 h) values were suppressed by 80% in non-uraemic subjects (P less than 0.01) from 218 +/- 47 nmol/l (at 2300 h) to 44 +/- 16 nmol/l (at 0800 h), whereas there was lack of suppression (P greater than 0.05) in values from uraemic subjects (224 +/- 36 nmol/l at 2300 h and 210 +/- 39 nmol/l at 0800 h). Irrespective of the degree of renal impairment in uraemic subjects, the 24 h UFC excretion was significantly greater (P less than 0.05) (1126 +/- 403 nmol/24 h) compared with non-uraemic subjects (342 +/- 94 nmol/24 h). These results confirm previous observations in Caucasians and reaffirm the existence of a pseudo-Cushingoid state in uraemia which may contribute to the associated hypertension and electrolyte abnormalities.