Heme Unit 13 - Iron deficiency Anemias

defects that cause microcytic anemia and clinical conditions associated with them

small RBCs often hypochromic, usually due to lack of hemoglobin synthesis

defective heme sythesis

less heme made → small RBCs

lack of iron → IDA

defective iron utilization → sideroblastic

prophyrias → genetic conditions

deficient globin synthesis

thalassemias

both production and destruction problem

cells form with inclusions leading to premature destruction

where is iron generally and quantity

hemoglobin (2/3 total body ~ 2.5g)

myoglobin (dependent on muscle mass)

cytochrome enzymes (all cells)

ferritin

hemosiderin

total body iron ~ 3.7g

total iron in the human body

3.7g

functional forms of iron

hemoglobin - carries O2

myoglobin

cytochrome

Transport forms of iron

Ferric iron (2+) binds to transferrin iron

2 Fe²⁺ per 1 transferrin

Storage forms of iron

Fe³⁺

Ferritin

Hemosiderin

Sources of iron

95% total body iron recycled

5% comes from diet

Mechanisms of iron loss

1 mg/day via desquamination, sweat, urine, bile, menstrual periods, pregnancy, nursing

Iron toxicity

Internal iron cannot be excreted

acute toxification → too much vitamin absorption

Oxidative states of iron

Storage iron: Ferric (Fe³⁺)

Metabloic/enzymatic: Ferrous (Fe²⁺)

How do we get iron in the body

its recycled or eaten

iron in food types

non-heme iron (ferric); grains and veggies

need enzyme to convert to ferrous state

harder to absorb

heme iron (ferrous); red meats

don’t need enzyme to convert so easier to absorb

How do we absorb iron

in the duodenum, picked up by transferrin

what happens if we don’t need iron

hepcidin from the liver shuts down ferroportin portals so blood doesn’t pick it up

iron hangs out in cells of small intestine until needed or shed off w/cells

How do we transport iron

transferrin brings it to bone marrow for heme synthesis or storage

cytochrome enzymes bring it to cells

Iron utilization/storage

Bone marrow - heme synthesis or stored as ferritin or hemosiderin and sent to necessary location

Ferritin

short term iron storage

in tissues/plasma

10-20% of total iron

does not stain with prussian blue unless clustered w/siderosomes

water soluble

½ made of protein (apoferritin)

Hemosiderin

Long term storage

in bone marrow and other tissues

5-10% of total iron

stains blue with prussian blue stain - appears yellow/brown when not stained

insoluble

50% is lipids, carbs, and protein

50% is iron including denatured ferritin

gender differences in iron storage

men have about 1000mg take about 8 years to go through all stores without absorption

women have about 300-500mg, lose about 30-40mg/month bc of menstruation

iron storage levels with disease conditions

Ferritin used first, then hemosiderin, once both depleted you are iron deficient

Conditions that result in iron deficiency

Malabsorption - celiac disease, achlorhydia, gastrectomy

Blood loss - heavy menstruation, GI bleeds; hemorrhoids, ulcers, colon cancer

Most common cause of iron deficiency in the USA

Blood loss