Iron

Question 1

distribution

Answer 1

1800 mg RBC
1000 mg liver
600 mg macrophages
300 mg bones
300 mg muscle
3 mg transferrin

Question 2

iron containing heme proteins

Answer 2

hemoglobin (for O2– Fe containing porphyrin ring)
myoglobin (O2 in cytoplasm of muscle cells)
cytochromes (electron carriers)

Question 3

Fe- S enzymes

Answer 3

aconitase

Question 4

iron storage and transfer proteins

Answer 4

transferrin (Fe carrying in plasma)
lactoferrin (Fe binding in milk)
ferritin and hemosiderin (storage form of Fe in cells)

Question 5

Functions

Answer 5

transport O2 in body, normal cell function, synthesis of hormones, connective tissue

Question 6

Absorption– Heme

Answer 6

heme iron- meats. 5-10% of dietary iron in western countries
bioavailability is 20-30%

binds to HCP1 –> intestinal cell

Question 7

Absorption– nonheme

Answer 7

plants (Fe3+)
(+) absorption:
(+) solubilization of Fe in food (stomach acid)
(+) reduction of Fe2+ (by VitC, Dcyt b- Fe3+ reductase) at mucosal surface of duodenum

(-) absorption:
phytates, polyphenols

Question 8

transport into intestinal cell

Answer 8

Heme: HCP1
nonheme: DMT1

Question 9

Storage

Answer 9

either stored as ferritin or transported across basolateral membrane –> circulation.

Question 10

Export

Answer 10

If Fe needed, passes into labile iron pool, processed for export by ferroportin (transport protein, IREG1). efflux of iron across basolateral surface of enterocytes to blood is achieved through coordinated action of ferroportin

Question 11

Ferroportin

Answer 11

transport Fe from inside cell–> out.

in enterocytes, hepatocytes, macrophages

Question 12

hepcidin

Answer 12

(-) ferroportin, traps iron inside intestinal cell

Question 13

hephaestin

Answer 13

(alpha ferroxidase) converts Fe2+ –> Fe3+, delivers iron to plasma transferrin

Question 14

Fe into Hgb by erythrocyte precursor cells: mechanism

Answer 14

• transferrin in plasma can bind 2 atoms of iron as Fe3+
• diferric transferrin– transferrin receptors (TfR) in cell surface
• TfR + transferrin –> cell, acidification –> Fe + transferrin (separated)
• Fe3+ –> Fe2+ –> out of endosome (DMT1)
• Fe2+ –> mitochondria –> Fe-Hgb + Fe-S proteins

Question 15

iron balance and excretion

Answer 15

fecal loss from shed enterocytes, extravasated RBCs, biliary heme breakdown products.
menstrual loss ~1.5 mg/d

Question 16

clinical outcomes of deficiency

Answer 16

low work performance, cognitive development, adverse pregnancy outcomes, difficulty maintaining body temp, low immune function, glossitis

Question 17

at risk

Answer 17

pregnant, infants, young children, heavy periods, freq blood donors, cancer, GI disease, heart failure, anemia of chronic dz

Question 18

Fe and heart disease

Answer 18

60% of patients w CHF have Fe deficiency, 17% IDA –> inc risk of death

Question 19

Fe and intense exercise

Answer 19

inc exercise –> inc RBC turnover, inc whole body Fe turnover

Question 20

Fe/Ca supplements

Answer 20

inc Ca –> low bioavailability of heme/ nonheme iron

Question 21

Stages of Fe depletion

Answer 21

mild deficiency/ storage iron depletion: low ferritin, low Fe in bone barrow

marginal deficiency/ mild functional deficiency/ iron deficient erythropoiesis: low iron stores, low plasma iron, low transferrin, inc STfR

Iron deficient anemia: (iron stores exhausted) low Hct, low Hgb, microcytic, hypochromic anemia

Question 22

3 types of anemias

Answer 22

microcytic: MCV <80, low Fe, Low Cu, low B6
normocytic MCV 80-100, protein calorie malnutrition
macrocytic MCV >100, low B12, folate