nutritional disorders
Selenium Toxicity
Introduction
Selenium(Se) is a part of the enzyme glutathione peroxidase, which metabolizes hydroperoxides formed from polyunsaturated fatty acids.Seleniumis also a part of the enzymes that deiodinate thyroid hormones. Generally,seleniumacts as an antioxidant that works withvitamin E. Plasma levels ofseleniumvary from 8 to 25 mcg/dL (0.1 to 0.3 micromoles/L), depending onseleniumintake. At high doses (>900 mcg/day),seleniumcauses toxicity. Symptoms ofseleniumtoxicity are mainly gastrointestinal disturbances (eg, nausea, diarrhea). Other manifestations include hair loss, abnormal nails, dermatitis, peripheral neuropathy,fatigue, irritability, and agarlicodor of the breath. Toxic levels of plasmaseleniumare not well defined. Diagnosisofseleniumtoxicity is usually clinical. Blood or urinaryseleniumlevels can be measured. Treatmentofseleniumtoxicity involves reducingseleniumconsumption. (See also Overview of Minerals .) 