“…It is worth noting a circadian variation in the urinary excretion of different solutes has been documented in healthy individuals: notably, the nocturnal excretion rates of potassium, sodium, chloride, and urate are only 50% of the rates observed during the light period [ 49 ], whereas phosphate reabsorption at night is more than that during the day [ 50 ]. Also, urinary pH and calcium showed a circadian variation in healthy subjects [ 51 ] In patients known to form stones; it has been demonstrated there is impaired circadian rhythmicity of urinary volume and some solutes excretion [ 52 , 53 , 54 , 55 , 56 ]. This was the first genetic polymorphism investigation to link the MTNR1A–biological melatonin system to calcium nephrolithiasis.…”