Exam 3 Iron/Porphyrin/Trace Elements Flashcards
(77 cards)
Distribution & function of iron throughout the body
- Hemoglobin 65% - oxygen delivery
- Myoglobin 10% - muscle oxygen
- Bound to enzymes 1-3% - cellular oxidative mechanism
How much iron does the body contain?
3-5g
Types of iron
• Heme – meats, especially organ meats
• Non-heme – plants & iron-fortified foods
o Spinach, beets, beans, almonds, bran flakes
Where is iron stored?
• Stored in bone marrow, spleen, liver
What are the storage forms of iron?
• Ferritin – soluble
1. Major iron storage protein found in all cells in body
2. Protein shell surrounding iron core
• Hemosiderin – insoluble
1. Found in cells of liver, spleen, bone marrow
How is iron transported?
• Plasma: transferrin
- Formed in liver
- Transports Fe3+ from GI tract and delivers to specific receptor sites
Iron RDA - ages 19-50
18mg/d
Iron RDA - ages 51+
8mg/d
Describe ferrous iron
2+
- absorbed form
- bound to protein: transferrin
Describe ferric iron
3+
- not easily absorbed
- dietary form
- needs to be reduced before it can be absorbed
- transport & storage form
What causes decreased levels of iron?
• Decreased availability o Inadequate intake, malabsorption • Increased need o Growth, premenopausal women, pregnancy • Chronic loss o Peptic ulcer, excessive menstruation, hemorrhoids, gastritis • Chronic diseases o Infections, inflammatory diseases
What causes increased levels of iron?
• Increased absorption
o Hemochromatosis, medication/iron supplements, dietary intake, transfusion
• Increased RBC destruction
• Disease
o Lead poisoning, pernicious anemia, megaloblastic anemia
What causes iron deficiency anemia?
Blood loss, inadequate intake, malabsorption
Describe transferrin, % saturation, and ferritin in IDA
Transferrin - increased
% saturation - decreased
Ferritin - <10ng/mL typical
Who is affected by IDA?
Children, women, pregnant women
What is hemosiderosis?
Secondary/acquired iron accumulation
No tissue damage, reversible
What causes hemosiderosis?
Iron supplements, blood transfusions
What is hemochromatosis?
- Hereditary disorder: mutation in HFE gene
- Iron accumulates in tissues leading to organ failure
- Irreversible
Symptoms of hemochromatosis
- Diabetes mellitus
- Bronzing of skin
- Sexual dysfunction
- Fatigue, weakness
- Manifests in middle age
What is a total iron test?
Reflects amount of ferric Fe3+ iron bound to transferrin
- Does not include free iron found in hemoglobin
What is TIBC test?
Amount of iron that could be bound if transferrin were saturated
- Typically, 1/3 of iron-binding sites are saturated
What is % saturation?
Transferrin saturation
- Normal range 15-50%
What is transferrin?
Negative-acute phase reactant
- Useful to diagnose hypo chromic anemias
- Measured by the amount of iron it can bind
What is ferritin?
Best diagnostic test for IDA
- Reflects iron stores
- Serves as acute-phase reactant
- Patients with inflammation or chronic infection may have increased ferritin
