Test 4 Flashcards
What is the most abundant trace element?
Iron
What is ferritin?
Storage form of iron
Decreased plasma ferritin is the earliest indication of what?
Iron deficiency
What does transferrin do?
Transports iron from GI tract to the bone marrow and other organs
Where is transferrin synthesized?
In the liver
Each transferrin molecule transports how many iron atoms?
two
What are some causes of increased serum iron?
Hemolytic anemias, thalassemias, hepatitis, excessive transfusions, iron poisoning (vitamin overdose)
What are some causes of decreased serum iron?
Insufficient dietary iron, bleeding, malabsorption, and infection or chronic disease
What is hemochromatosis?
A recessive genetic disorder where excess iron accumulates in tissues from increased GI absorption
What is treatment for hemochromatosis?
Therapeutic phlebotomy
What are the main steps iron tests follow?
Dissociate Fe from transferrin
Reduce Fe from ferric to ferrous
Add ferrozine to make a colored compound
Measure colored product by spectrophotometry
What specimen is needed for iron testing?
Serum with no hemolysis or has been in a tube with anticoagulants that bind iron (EDTA and Sodium Citrate)
What is the TIBC?
Total Iron Binding Capacity is an estimate of transferrin concentration
What does TIBC measure?
How much iron could be transported in the plasma by transferrin (not how much iron the patient has)
TIBC is an ________ measurement of transferrin.
Indirect
What are the steps for TIBC testing?
- Add excessive amount of iron to serum to saturate transferrin.
- Add MgCO3 to remove unbound iron
- Centrifuge specimen to get the MgCO3 to the bottom
- Take the supernate and test that for iron
What 3 components are in an iron profile?
Total iron, TIBC, % iron saturation
% Iron Saturation = ?
Total Iron / TIBC X 100
What does the % Iron saturation measure?
Measures how full transferrin is
What are the usual results for total iron, TIBC, and %Fe Sat in a person with iron deficiency?
Total iron decreased
TIBC increased
% Fe Sat decreased
What are the usual results for total iron, TIBC, and %Fe Sat in a person with hemochromatosis?
Total iron increased
TIBC decreased
% Fe Sat increased
What are the usual results for total iron, TIBC, and %Fe Sat in a person with infection/cancer?
Total iron decreased
TIBC decreased
% Fe Sat increased
What are the usual results for total iron, TIBC, and %Fe Sat in a person with hemolysis?
Total iron increased
TIBC normal
% Fe Sat increased
What is step 1 and 2 in the formation of bilirubin?
- RBCs are eaten by spleen. Hgb is catabolized into amino acids, iron, and heme
- Heme ring is broken open and converted to unconjugated bilirubin
What are steps 3 and 4 in the formation of bilirubin?
- RE cells in the spleen secrete the unconjugated bilirubin into the plasma, where bilirubin is bound by albumin.
- Albumin - bilirubin complex travels to liver
What are steps 5 and 6 in the formation of bilirubin?
- Hepatocytes conjugates bilirubin with glucoronic acid by UDPG enzyme
- Conjugated bilirubin is secreted into bile duct
What are step 7 and 8 in the formation of bilirubin?
- GI bacterial normal flora converts conjugated bilirubin into urobilinogen
- Urobilinogen may be excreted into stool, reabsorbed in plasma, or excreted in the urine.
What is UDPGs main job?
Conjugating bilirubin
What two things can increased plasma bilirubin indicate?
Increased RBC catabolism or decreased hepatic conjugation with excretion of bilirubin
What is jaundice?
Yellowing of the skin and sclera from increased bilirubin