Skip navigation | ||
|
||
Medical Encyclopedia |
|
Other encyclopedia topics: | A-Ag Ah-Ap Aq-Az B-Bk Bl-Bz C-Cg Ch-Co Cp-Cz D-Di Dj-Dz E-Ep Eq-Ez F G H-Hf Hg-Hz I-In Io-Iz J K L-Ln Lo-Lz M-Mf Mg-Mz N O P-Pl Pm-Pz Q R S-Sh Si-Sp Sq-Sz T-Tn To-Tz U V W X Y Z 0-9 |
Contents of this page: | |
|
|
|
Alternative names Return to top
UroporphyrinDefinition Return to top
This is a test that measures the level of porphyrins in urine.How the test is performed Return to top
A 24-hour urine sample is needed. The health care provider will instruct you, if necessary, to discontinue drugs that may interfere with the test.How to prepare for the test Return to top
The health care provider may advise you to discontinue drugs that can affect the test. (See "Special considerations.")How the test will feel Return to top
The test will feel the same as normal urination.Why the test is performed Return to top
This test is most often performed when porphyria or other disorders that can cause abnormal urine porphyrins is suspected.
The most important function of porphyrins is as components of heme. Heme is made from iron + protoporphyrin. Hemoglobin is made up of four heme molecules + four globin proteins. Oxygen binds to the iron in the heme molecules.
Various kinds of porphyrins exist with the same basic structure, but with slightly different chemical appearance.
Heme production involves biochemical conversion of porphyrins into delta-ALA, then to PBG, then uroporphyrin, then coproporphyrin, then protoporphyrin, and finally into the end product -- heme.
Each of these steps requires the presence of a specific enzyme. If any of the enzymes are deficient (because of a genetic disease or interference by a toxic substance), the intermediate substances build up, and a type of porphyria results.
Normal Values Return to top
What abnormal results mean Return to top
Increased levels of urinary PBG may indicate:In specific types of porphyria, levels of ALA, uroporphyrin, and coproporphyrin may also be higher than normal.
What the risks are Return to top
There are no risks.Special considerations Return to top
Drugs that can affect test measurements include aminosalicylic acid, birth control pills, barbiturates, chloral hydrate, chlorpropamide, ethyl alcohol, griseofulvin, morphine, phenazopyridine, procaine, and sulfonamides. Update Date: 6/1/2003 Updated by: Marcia S. Brose, M.D., Ph.D., Division of Hematology/Oncology, Hospital of the University of Pennsylvania, Philadelphia, PA. Review provided by VeriMed Healthcare Network.
Home | Health Topics | Drug Information | Encyclopedia | Dictionary | News | Directories | Other Resources | |
Copyright | Privacy | Accessibility | Selection Guidelines U.S. National Library of Medicine, 8600 Rockville Pike, Bethesda, MD 20894 National Institutes of Health | Department of Health & Human Services |
Page last updated: 28 October 2004 |