The are 2 principal goals in this study:

1. To measure plasma copeptin levels in healthy subjects and to correlate them with plasma AVP concentrations and urine osmolalities in iso-, hypo-, and hyperosmolar states.
2. To measure plasma copeptin concentrations in patients with chronic renal failure under the same conditions described above, in order to characterize the impact of renal function on circulating copeptin levels in correlation to plasma AVP and urine osmolality.

Inclusion Criteria:

• chronic renal failure grade I through IV
• healthy age-matched controls

Exclusion Criteria:

• chronic renal failure grade V
• heart failure
• liver disease
• nephrotic syndrome
• anemia (hemoglobin level < 100 g/L)
• uncontrolled hypertension (systolic BP > 160 mmHg; diastolic BP > 95 mm Hg)
• coexisting severe disease
• known thyroid disease
• known hypocortisolism
• known hypercortisolism
• known diabetes insipidus
• pregnancy
• lactation

Healthy volunteers; patients with chronic renal failure