839 INTEGUMENTARY LOSS OF CALCIUM

Abstract

The amount of integumentary calcium loss has been generally considered very small and therefore, has rarely been included in calcium metabolic studies. During our study of calcium and protein metabolism, two conditions of integumentary calcium loss were measured. The first, collected over a six-day period represented dermal loss by an ambulatory but rather sedentary man. The second was collected over a 40 minute period of strenous exercise. The daily loss of 16 subjects in 52 determination of six-day periods each was 8.7 ± 1.9 mg/m2/day. The amount was not influenced by calcium intake (0.1 to 2.3 g/day). In contrast to urinary calcium excretion, which is directly related to protein intake, there was no significant change by varing protein intake (1 to 96 g nitrogen/day). No compensatory relationship between urinary and integumentary calcium excretion was noted. During strenous exercise calcium loss increased to to 25 mg (11 to 45 mg) in 40 minutes. There was no compensatory decrease in urinary excretion on the day of strenous exercise. It was also noted that this calcium loss was not affected by general calcium balance. The amount of integumentary loss may become even greater than the urinary calcium excretion. We conclude that integumentary calcium loss probably should be considered in calcium metabolic studies.