Week 10 - Visit 6 - Study Day 1 - Patients will be admitted to the GCRC as an inpatient. They will be asked to lie supine for 24 hours with the head of their bed no higher than 10 degrees. They will have an interval history and physical. An IV catheter will be placed. After an initial void, they will begin a 24 hour urine creatinine, sodium and aldosterone. They will have a baseline BMP, high sensitivity C-Reactive Protein (hsCRP) and CBC. They will have blood drawn every 3 hours for PAI-1 antigen levels, plasma renin activity, plasma ACE activity, plasma aldosterone levels, plasma cortisol and melatonin. White blood cells will be harvested in PaxGene tubes for future extraction of white blood cell mRNA. They will be on a eucaloric, low sodium diet. At the end of the study day they will remain on their home medications, HCTZ (25mg po, qd), however they will stop their current blinded study medication (aliskiren or placebo). Subjects will have DNA banked from unused blood buffy coats. If applicable, UA pregnancy test will be performed by CRC nurses on admission.