Hydroxyproline can be made by the body, or more specifically in the liver from other amino acids, making it a non-essential amino acid. It is used in structural proteins such as collagen and connective tissue. Proline is converted to hydroxyproline but the action requires the presence of vitamin C. A deficiency in vitamin C may also cause a deficiency of hydroxyproline.
Hydroxyproline is necessary for the construction of the body's major structural protein, collagen. Defects in collagen synthesis lead to easy bruising, internal bleeding, breakdown of connective tissue of the ligaments and tendons, and increased risk to blood vessel damage. Increased spill of hydroxyproline in the urine is generally associated with breakdown of connective tissue due to disease process and may also be a manifestation of vitamin C deficiency.