Seasonal variation of urinary calcium and oxalate excretion, serum 25(OH)D3 and albumin level in relation to renal stone formation.

Seasonal variations in urinary calcium and oxalate excretion, serum 25(OH)D3 and albumin level were studied in 11 normo- and 11 hypercalciuric renal stone-formers, in 10 healthy subjects and in 14 long-stay hospital patients during one year. Serum albumin levels increased significantly during May--October in all four groups, whereas no significant changes occurred in serum calcium values when adjusted for differences in serum albumin concentration. Serum 25(OH)D3 level, urinary calcium and oxalate excretion were significantly higher during May--October than November--April in all except the long-stay hospital patients, whose corresponding values showed no seasonal changes and whose serum 25(OH)D3 levels as well as urinary calcium excretion were significantly lower than in the other three groups. The serum 25(OH)D3 level was significantly higher throughout the year in hypercalciuric than normocalciuric stone-formers. The hypercalciuric patients also passed more stones than the normocalciuric patients during a period of 9 years. There was a positive correlation between serum 25(OH)D3 and urinary calcium, between serum 25(OH)D3 and stone episodes and between urinary calcium and stone episodes. Because of this positive correlation, it might be useful to concentrate preventive therapy for recurrent renal stones to the light period only.