Selenium (Se) is a part of the enzyme glutathione peroxidase, which metabolizes hydroperoxides formed from polyunsaturated fatty acids. Selenium is also a part of the enzymes that deiodinate thyroid hormones. Generally, selenium acts as an antioxidant that works with vitamin E.
Plasma levels of selenium vary from 8 to 25 mcg/dL (0.1 to 0.3 micromoles/L), depending on selenium intake.
At high doses (> 900 mcg/day), selenium causes toxicity.
Symptoms of selenium toxicity are mainly gastrointestinal disturbances (eg, nausea, diarrhea). Other manifestations include hair loss, abnormal nails, dermatitis, peripheral neuropathy,fatigue, irritability, and a garlic odor of the breath.
Toxic levels of plasma selenium are not well defined.
Diagnosis of selenium toxicity is usually clinical. Blood or urinary selenium levels can be measured.
Treatment of selenium toxicity involves reducing selenium consumption.
(See also Overview of Mineral Deficiency and Toxicity.)
