A metallic element chemically similar to sulfur, atomic no. 34, atomic wt. 78.96; an essential trace element toxic in large quantities that is required for glutathione peroxidase and a few other enzymes; 75Se (half-life equal to 119.78 days) is used in scintography of the pancreas and parathyroid glands.
[G. selene, moon]
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Examples: glitazone, GI cocktail, etc.