Biochemical and hormonal parameters Blood samples were collected between 7:00 and 8:00 a.m. after an overnight fast, and before dialysis in CKD-HD patients. Routine biochemical parameters [creatinine, urea] were measured in all subjects. Glomerular filtration rate was estimated (eGFR) by the Schwartz formula, with k = 0.413, as appropriate for standardized creatinine.