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Carotenes are the major precursors of vitamin A found in most yellow, orange, and dark green vegetables. Mucosal cells of the small intestine convert each molecule of carotene into two molecules of vitamin A. Excess vitamin A is stored in the liver. Vitamin A is fat-soluble and is absorbed with lipid. Any condition associated with steatorrhea such as pancreatic insufficiency or biliary obstruction can lead to carotene deficiency. Low levels are also associated with liver disease, dietary deficiency, protein energy malnutrition, high fever, stress, burns, and infections. Elevations are seen in hypothyroidism, excessive dietary intake, and hyperlipidemia associated with diabetes mellitus or nephrotic syndrome. Reference range is 48 200 ug/dL. Values for children up to one year are approximately twice those of adults. Specimen requirement is one plain red top tube of blood. The specimen should be drawn after an overnight (12 - 14 hours) fast. The patient should not consume alcohol during the preceding 24 hours. The tube must be refrigerated and protected from light. |
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