Seasonal variations in urinary excretion of calcium.

A retrospective study over a three-year period has shown a noticeable seasonal variation in the daily urinary excretion of calcium in healthy men, healthy women, and men prone to form stones. This reached a maximum in July or August and a minimum in December or January in all three groups. For any given month the stone formers had higher urinary calcium values than healthy men, who, in turn, had higher values than healthy women.