Vitamin A (Retinol), Serum

Vitamin A has a number of important functions throughout the body. These include visual cycle, growth and differentiation of epithelial tissues and bone, reproduction and embryonic development. Ingested vitamin A enters the circulation mainly as long-chain fatty acid esters (retinyl esters) in the chylomicron fraction. Most of the retinol is then stored in the liver in esterified form. The release from the hepatocytes requires the association of retinol with retinol binding protein. Deficiency of vitamin A, an essential component of rhodopsin in the eye leads to night blindness. Severe, prolonged deficiency results in degeneration of retinal pigment epithelium and photoreceptors, conjunctival and corneal keratinisation.

Any condition that interferes with ingestion, absorption, storage or transport of vitamin A can lead to a deficiency in target tissues. Nutritional vitamin A deficiency has been known for a long time with the major symptom being night blindness. Conjunctival xerosis (dry conjunctiva) is a less common feature of vitamin A deficiency.

1 ml EDTA plasma Protect From Light

Fasting samples are preferred.