Does twenty-four-hour biological variation of serum creatinine and cystatin C influence GFR estimation?

In the evolution process, moving from the marine environment challenged organisms to adapt to terrestrial conditions. This increased the requirement of the kidney regarding urine concentration abilities and tubular reabsorption of solutes, while coping with day/night cycles (1). In this sense, glomerular filtration rate (GFR) and tubular function were proved to be strongly related to a circadian rhythm (2).