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In 40 healthy persons, 11 nondialyzed uremic patients and 27 dialyzed uremic patients, of whom 4 also had cancer, the selenium concentration in serum was determined. The mean serum selenium concentration in healthy persons was 13.6 ± 0.8 μg/dl, in nondialyzed patients 11.9 ± 1.9 μg/dl and in dialyzed uremic patients 11.3 ± 1.0 μg/dl. There was a significant statistical difference between healthy persons and uremic patients (p < 0.00l), but not between dialyzed and nondialyzed uremic patients. The subgroup of cancer patients on hemodialysis also had low serum selenium concentrations. The possible role of low selenium levels as one of the factors responsible for the increased incidence of malignancy in patients with chronic renal failure is supported by several facts such as: (a) low serum selenium levels detected in patients with malignant diseases; (b) the higher cancer incidence in inhabitants of low-selenium areas, and (c) the known ability of selenium to inhibit many types of experimental carcinogenesis.

Trace element selenium (Se) is regarded to be a breast cancer preventive factor involved in multiple protective pathways. In all, 80 women with breast cancer who underwent a radical mastectomy were enrolled in the study. Serum Se and carcinoembryonic antigen levels were measured using a fluorometric and IRMA assay, respectively. Se tissue concentration was determined by a tissue extracting fluorometric assay. For statistical analysis purposes t -test was used and P -values <0.001 were regarded as statistically significant. Serum Se was 42.5±7.5 μ g l −1 in breast cancer patients and 67.6±5.36 μ g l −1 in the age-matched control group of healthy individuals. Serum carcinoembryonic antigen in patients was 10±1.7 U ml −1 (normal <2.5 U ml −1 in nonsmokers/<3.5 U ml −1 in smokers). A statistically significant difference was found for both serum Se and CEA between two groups studied ( P <0.001). Neoplastic tissue Se concentration was 2660±210 mg g −1 tissue; its concentration in the adjacent non-neoplastic tissue was 680±110 mg g −1 tissue ( P <0.001). An inverse relationship between Se and CEA serum levels was found in the two groups studied ( r =−0.794). There was no correlation between serum/tissue Se concentration and stage of the disease. The decrease in serum Se concentration as well as its increased concentration in the neoplastic breast tissue is of great significance. These alterations may reflect part of the defence mechanisms against the carcinogenetic process.

This study indicates that there is a cyclic fluctuation of Cu and Zn concentrations in plasma during the menstrual cycle, in healthy eumenorrhoic women. This cyclic fluctuation might be due to the cyclic fluctuation of plasma levels of E2.