Synonyms: Urinary hydroxyproline
Clinical significance
Hydroxyproline makes up about 10% of collagen and, since collagen is the protein component of bone, its excretion in the urine is directly proportional to the amount of bone broken down in the normal turnover of this tissue. Since it is also found in the collagen of other tissues (e.g. skin), measuring urinary hydroxyproline excretion is relatively non-specific.
Clinical indications
Assessment of bone resorption (osteoporosis, Paget’s disease); assessment of response to treatment.
Sample type
A 24-hour urine collection is required.
Preparation
The patient must follow a collagen-free diet the day before and during the collection: avoid meat, fish, game, meat extracts and stocks, ice cream, desserts and other products containing gelatine. If this is not possible, follow a low-collagen diet: no more than 100 g of meat a day, with cartilage and tendons removed. The patient’s weight and height must be known.