AQP2 and inappropriate ADH syndrome: An increase in the urinary release of AQP2 has been reported in patients with SIADH (syndrome of inappropriate secretion of anti-diuretic hormone), cognitive heart failure, or hepatic cirrhosis, and in pregnant women, while a decrease in the urinary release of AQP2 was reported in patients with chronic kidney diseases (including polycystic kidney) and patients treated with a V2 receptor antagonist40–42.