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Hypervitaminosis A

Hypervitaminosis A refers to the toxic effects of ingesting too much preformed vitamin A (retinyl esters, retinol, and retinal). Symptoms arise as a result of altered bone metabolism and altered metabolism of other fat-soluble vitamins. Hypervitaminosis A is believed to have occurred in early humans, and the problem has persisted throughout human history. Toxicity results from ingesting too much preformed vitamin A from foods (such as fish liver or animal liver), supplements, or prescription medications and can be prevented by ingesting no more than the recommended daily amount. Diagnosis can be difficult, as serum retinol is not sensitive to toxic levels of vitamin A, but there are effective tests available. Hypervitaminosis A is usually treated by stopping intake of the offending food(s), supplement(s), or medication. Most people make a full recovery. High intake of provitamin carotenoids (such as beta-carotene) from vegetables and fruits does not cause hypervitaminosis A. Symptoms may include: Changes in consciousness Decreased appetite Dizziness Vision changes, double vision (young children) Drowsiness Headache Irritability Nausea Poor weight gain (infants and children) Skin and hair changes Cracking at corners of the mouth Hair loss Higher sensitivity to sunlight Oily skin and hair (seborrhea) Skin peeling, itching Vomiting Yellow discoloration of the skin (aurantiasis cutis) Signs Abnormal softening of the skull bone (craniotabes—infants and children) Blurred vision Bone pain or swelling Bulging fontanelle (infants) Gastric mucosal calcinosis Heart valve calcification Hypercalcemia Increased intracranial pressure manifesting as cerebral edema, papilledema, and headache (may be referred to as Idiopathic intracranial hypertension) Liver damage Premature epiphyseal closure Spontaneous fracture Uremic pruritus Hypervitaminosis A results from excessive intake of preformed vitamin A. Genetic variations in tolerance to vitamin A intake may occur, so the toxic dose will not be the same for everyone.

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Related concepts (10)
Retinoid
The retinoids are a class of chemical compounds that are vitamers of vitamin A or are chemically related to it. Retinoids have found use in medicine where they regulate epithelial cell growth. Retinoids have many important functions throughout the body including roles in vision, regulation of cell proliferation and differentiation, growth of bone tissue, immune function, and activation of tumor suppressor genes. Research is also being done into their ability to treat skin cancers.
Provitamin
A provitamin is a substance that may be converted within the body to a vitamin. The term previtamin is a synonym. The term "provitamin" is used when it is desirable to label a substance with little or no vitamin activity, but which can be converted to an active form by normal metabolic processes. Some provitamins are: "Provitamin A" is a name for β-carotene, which has only about 1/6 the biological activity of retinol (vitamin A); the body uses an enzyme to convert β-carotene to retinol.
Liver
The liver is a major metabolic organ only found in vertebrate animals, which performs many essential biological functions such as detoxification of the organism, and the synthesis of proteins and biochemicals necessary for digestion and growth. In humans, it is located in the right upper quadrant of the abdomen, below the diaphragm and mostly shielded by the lower right rib cage. Its other metabolic roles include carbohydrate metabolism, the production of hormones, conversion and storage of nutrients such as glucose and glycogen, and the decomposition of red blood cells.
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