Vitamin A is a vital nutritional component. If this is not supplied to the body, deficiency symptoms (hypo-/avitaminosis) occur. Different forms of vitamin A can be distinguished:
- Vitamin A1 (retinol)
- Vitamin A2 (3-dehydroretinol)
- And other derivatives
Vitamin A is absorbed in the human body in the duodenum (duodenum) and in the upper jejunum (empty intestine). It is stored in the liver and bound to protein (retinol-binding protein – RBF) transported in the blood. Vitamin A is fat-soluble and is inactivated mainly by oxygen, but also by UV light. It is mainly found in dairy products, egg yolk, liver and in many fruits and vegetables – there as provitamin (carotenoids). An important task of vitamin A is the maintenance of vision, especially twilight/night vision. But it also plays an important role in metabolism as well as in growth (regulation of bone growth) and sexual development. Vitamin A has another important role as a protective substance for the ectoderm (e.g. epithelial cell regeneration of mucous membranes).
The process
Material needed
- Blood serum
Preparation of the patient
- Not necessary
Disruptive factors
- The blood sample must be stored in the dark
Standard values
Value in μg/l | Value in μmol/l | |
Vitamin A deficiency | < 100-200 | < 0,35- 0,7 |
Normal range | 100-1.000 | 0,35- 3,5 |
Vitamin A overdose | > 1.000-2.000 | 3,5- 7 |
Indications
- Suspicion of vitamin A deficiency (because of malabsorption (Crohn’s disease, short bowel syndrome, celiac disease, etc.) or maldigestion (bile acid deficiency, lipase deficiency, exocrine pancreatic insufficiency) or clinical symptoms of deficiency).
- Vitamin A overdose
Interpretation
Interpretation of increased values
- Vitamin A overdose during vitamin A therapy (e.g., because of acne (e.g., acne vulgaris), psoriasis); the following symptoms may occur:
- Alopecia (hair loss)
- Anorexia nervosa (anorexia)
- Arthralgia (joint pain)
- Cephalgia (headache)
- Cheilitis (inflammation of the lips)
- Dysosmia (olfactory disorders)
- Nausea (nausea)/vomiting
- Periosteal swelling – thickening of the periosteum.
- Irritability
- Visual disturbances
- Xeroderma (dry skin) – dry, red, scaly skin.
Interpretation of lowered values
- Alimentary (nutritional)
- Unilateral nutrition (parenteral nutrition)
- Chronic high alcohol consumption
- Malabsorption (disorder of absorption)
- Chronic inflammatory bowel disease such as Crohn’s disease.
- Infection with lamblia (small intestinal parasites).
- Ileojejunal bypass
- Short bowel syndrome – malabsorption after extensive small bowel resection – partial removal of the small bowel.
- Celiac disease (gluten-induced enteropathy) – chronic disease of the mucosa of the small intestine (small intestinal mucosa), which is based on hypersensitivity to the cereal protein gluten.
- Maldigestion (disorder of digestion).
- Bile acid deficiency
- Exocrine pancreatic insufficiency – inability of the pancreas to produce sufficient digestive enzymes (determination: elastase in stool).
- Lipase deficiency
- Diseases that may be associated with decreased serum vitamin A levels.
- Malformations associated with vitamin A deficiency during pregnancy.
- Follicular hyperkeratosis (“toad skin“) – cornification disorder.
- Premature
- Glossitis (inflammation of the oral mucosa)
- Bone formation disorders
- Liver cirrhosis – connective tissue remodeling of the liver with functional impairment.
- Nephrotic syndrome – complex of symptoms in various kidney diseases leading to increased permeability of membranes.
- Nycteralopia (night blindness).
- RBF deficiency (retinol-binding protein).
- Growth disorders
- Xeroderma – dry skin
- Xerophthalmia – dry eyes
- Increased need
- Pregnant women / breastfeeding
Further notes
- The normal requirement for vitamin A is 0.8 mg/d for women and 1.0 mg/d for men.
Attention. Note on the state of supply (National Consumption Study II 2008) 15% of men and 10% of women do not reach the recommended daily intake. Particularly affected are 14-18 year old men and women.