Seasonal variation of urinary excretion of total metanephrines

Results of 1414 measurements of urinary excretion of free and conjugated (total) metanephrine and normetanephrine (total metanephrines, tMN) and of 1630 measurements of vanilmandelic acid (VMA) excretion were analysed according to the month of sample collection. These collections had been carried out as a part of a study of hypertension at out institute over the 5-year period between 1970 and 1975. The means and scatters of tMN were significantly varied depending on the season of the year; the mean during 3 months of summer was 380 mug/day and the mean for 3 winter months 800 mug/day. The scatter of tMN in winter months was wider. A minor seasonal variation was observed for VMA: the means of summer and winter months were 3.8 mg/day and 4.5 mg/day, respectively. The results suggest a seasonal difference of catecholamine catabolism.