Iron Deficiency and Anaemic of Chronic Disease Flashcards
how is most iron in the body found as?
Hb
what sort of iron is found in HB?
ferrous in the haem part
role of holding onto oxygen
haem is made of a protoporphyin ring with an iron atom in the centre
how much iron needs to be consumed daily to replace the loss of red cells?
20 mg
how is iron lost by the body?
desquamated cells of the skin and gut
bleeding (menstruation)
where in the diet can iron be found?
red meat offal fish vegetables whole grain cereal chocolate
how much iron is lost by men and women per day?
men: ~1mg a day
women: ~2mg a day
why is most consumed iron not absorbed?
the body can not absorb Fe3+ (ferric) only ferrous (Fe2+) is absorbed
haem is better absorbed than free iron in general (10% compared to 1-2%)
what drink can enhance Fe2+ absorption?
orange juice (acid pH, ascorbic acid)
what drink can decrease Fe2+ absorption?
tea (alkaline pH, phytates and phosphates)
it converts iron to its ferric form and can lead to chronic low levels of ferrous
what are the3 factors that affect the absorption of iron?
diet intestine (acid) systemic (iron def)
what 3 things lead to an increase in iron absorption?
- iron deficiency
- anaemia/hypoxia
- pregnancy
what protein facilities the transport of iron into the blood?
ferroportin
which molecule inhibits the channel transporting iron into the blood?
hepcidin inhibits ferroportin
where can ferroportin be found?
enterocytes of duodenum
macrophages of the spleen
hepatocytes
what is iron from the diet (in the lumen) converted to intracellularly?
ferritin
how is the newly produced ferritin carried in the blood?
bound to transferrin in the plasma
where is transferrin produced?
what is normal transferrin saturation with iron?
produced in the liver (glycoprotein)
20-40%
what are the 3 measurements made with iron?
Total Iron Binding capacity (TIBC)
Transferrin Saturation
Transferrin Level
how is iron absorbed at the site required?
as transferrin cannot enter directly, it binds to the Tf-R and is taken up altogether
when is iron released by transferrin when endoctyosed as a complex?
with a drop in pH
transferrin receptors can be recycled at this point
what is the purpose of iron binding to transferrin?
iron is toxic and insoluble
there is no excretion system for iron
where is EPO produced?
kidneys
in response to what is EPO production increased?
hypoxia triggering more RBC precursors to be releases
these precursors survive longer and will eventually grow and differentiate
in which patients is ACD seen?
in patients with chronic disease
they dont show the classic causes of anaemia (no obvious cause)
what are the lab signs of ACD?
o Higher levels of C-reactive protein – an acute phase protein (inflammation/infection).
o Higher Erythrocyte Sedimentation Rate (ESR) – rises in inflammation/infection.
o An acute phase response and increases in: ferritin, Factor VIII, fibrinogen and IG.
i.e. high CRP, high ESR indicate ACD
what conditions are associated with ACD?
o Chronic infections – e.g. TB/HIV.
o Chronic inflammation.
o Malignancy.
o Misc. – e.g. cardiac failure.
what is the main pathogenesis mechanism of ACD
cytokine release
TNF alpha and IL
interference with iron transport
how do cytokines lead to ACD?
- prevent usual flow of iron from the duodenum to the red cells i.e. block iron utilisation
- stop EP increase
- increase ferritin production
- increase RBC death therefore reduced RBC production, and less iron available
cytokines affect iron transport
what is the major cause of iron def?
blood
bleeding e.g. menstrual or GI bleed
what are the minor causes of iron def?
- increase use of iron e.g. pregnancy/ growth
- dietary def e.g. vegetarian
- malabsorption e.g. coeliac disease
when are full GI investigations carried out for iron def?
- males
- women over 40, post-menopausal
- woman with scanty menstrual loss
what makes up a full GI investigation ?
upper GI endoscopy (oesophagus, stomach, duodenum)
duodenal biopsy
colonoscopy
if nothing is found a small bowel meal is given
when is no investigation done?
- a menstruating women <40 with heavy periods
- multiple pregnancies
- no GI symptoms
what also can be investigated to find the cause of iron def?
urinary blood loss (renal tract)
antibodies for coeliac disease
bleeding cancers (chronic, low grade)
what are the lab parameters in blood tests that would be useful in investigation?
- serum iron
- total iron binding capacity
- transferrin saturation
- serum ferritin
- haemosiderin in bone marrow using Prussian blue solution
- MCV
causes of low MCV [3]
iron def
thalassemia trait
ACD
serum levels in the causes of low MCV
iron def has low serum Fe
ACD has low serum Fe
thala. trait has normal Fe
ferritin levels in the causes of low MCV
iron def has low ferritin
ACD has high ferritin (due to interfered transportation, nothing is moved from ferritin)
why is ferritin not reliable in telling whether someone has iron def?
it could also mean they have underlying ACD (high ferritin level) e.g. RA with bleeding ulcer
a raised CRP and ESR would indicate an underlying condition
transferrin levels in the causes of low MCV
- iron def has a transferrin increase (attempt to use)
- ACD has normal or low transferrin (little transport)
transferrin saturations in causes of low MCV
- iron def has low transferrin sat (more transferrin, less iron)
- ACD has normal transferring sat (iron and transferrin both decrease so sat is normal)
further investigation to blood test
Endoscopy and colonoscopy. Duodenal biopsy. Anti-helicobacter antibodies. Anti-coeliac antibodies. Other – abdominal ultrasound to look at kidneys, dipstick urine, pelvic US to exclude fibrosis.
thalassemia trait parameter results:
serum iron-
ferritin-
TIBC- (same as transferrin level)
serum iron- NORMAL
ferritin- NORMAL
TIBC- NORMAL
Hb- LOW
MCV- LOW
transferrin- NORMAL
transferrin sat- NORMAL
classic ACD parameter results:
serum iron-
ferritin-
TIBC- (same as transferrin level)
serum iron- LOW
ferritin- HIGH OR NORMAL
TIBC- NORMAL OR LOW
Hb- LOW
MCV- LOW OR NORMAL
transferrin- NORMAL OR LOW
transferrin sat- NORMAL
classic iron def parameter results:
serum iron-
ferritin-
TIBC-
serum iron- LOW
ferritin- LOW
TIBC- HIGH
Hb- LOW
MCV- LOW
transferrin- HIGH
transferrin sat- LOW
how much iron in an adult?
3-5grams
what are the 3 pools that iron can be located in?
1) metabolic pool: Hb and myoglobin (2-3g)
2) storage pool: ferritin and haemosiderin (1g)
3) transit pool: plasma protein bound (transferrin bound) (3mg)
what is iron a positive regulator for?
what is it a negative regulator for?
positive for erythropoiesis and ferritin genes
negative for transferrin receptor gene (transferrin receptor located on red blood cells)
i.e. iron is pro storage, doesn’t want to be moving much
what is irons interaction with transferrin receptor?
the iron complexes with the receptor and is internalised into the erythroblast
transferrin is recirculated once iron is removed from it
hypochromic microcytic anaemia
- less Hb (therefore low MCH)
- lower concentration of Hb (hence hypochromic, low MCHC)
- microcytic due to low MCV
what are the 3 commonest reasons for hypochromic microcytic anaemia?
1) iron deficiency
2) thalassemia
3) anaemia of chronic disease
milder forms of thalassemia cause microcytosis without the anaemia
what is the major cause of iron deficiency ?
blood loss
due to menstruation
due to gastrointestinal
what are the other causes of iron def apart from bleeding?
- dietary deficiency
low dietary intake in vegans and vegetarians - increased needs
pubertal growth
during child bearing - malabsorption (less common)
menstruating women and growing children usually have poor diet as a cause of iron def
what oral iron compound is commonly used for iron replacement treatment?
ferrous sulphate (high iron content)
what are the side effects of ferrous sulphate?
- constipation
- indigestion
these reduce compliance
therefore ferrous fumarate or ferrous gluconate with less iron may be better tolerated
may need to be given parenterally
how does SERRUM FERRITIN help distinguish the different causes of anaemia
1) uncomplicated iron deficiencies –> LOW serum ferritin
2) thalassemia trait–> NORMAL serum ferritin
3) ACD–> RAISED or NORMAL serum ferritin
As ferritin is an acute phase reactant, however, it may be normal or increased in patients where iron deficiency co-exists with chronic inflammatory conditions.
what is Anaemia of Chronic Disease associated with?
chronic inflammatory, infectious or neoplastic condition
what sort of anaemia does ACD usually cause?
mild-moderate normocytic/microcytic hypochromic anaemia
what are the inflammatory markers of ACD?
- C-reactive protein
- ESR (erythrocyte sedimentation rate)
both of these are raised
why does ACD causes hypochromia?
failed incorporation of iron into erythroblast causes reduced Hb synthesis
what are serum ferritin levels in those with ACD AND IDA?
low in the normal range
how can ACD and IDA be distinguished?
bone marrow aspirate