vitamin A, a fat-soluble, solid terpene alcohol essential for skeletal growth, maintenance of normal mucosal epithelium, reproduction, and visual acuity. It is derived from various carotenoids, mainly beta-carotene, and is present in leafy green vegetables and yellow fruits and vegetables as a precursor and is found preformed in fish-liver oils, liver, milk, cheese, butter, and egg yolk. Deficiency leads to atrophy of epithelial tissue resulting in keratomalacia, xerophthalmia, night blindness, and lessened resistance to infection of mucous membranes. Symptoms of hypervitaminosis A are irritability, fatigue, lethargy, abdominal discomfort, painful joints, severe throbbing headache, increased intracranial pressure, insomnia and restlessness, night sweats, loss of body hair, and brittle nails. Also called antiinfection vitamin, antixerophthalmic vitamin.
