12. Anaemia 1 Flashcards
Describe the levels of iron absorbed in the body compared to the levels that are consumed/excreted
Average diet contains 15mg of iron per day
About 1mg of iron is absorbed by the body
SO about 14mg of iron from the diet will be excreted
Where in the body is iron absorbed?
Majority of iron is absorbed from digested food in the duodenum via enterocytes located in the duodenal lining
These enterocytes have transporter proteins in the microvilli and these allow them to move iron into the body
What are the different forms of iron that can enter the body from the diet and how is this absorbed in the body?
Iron can be in the form of haem e.g. from meat - this is from the myoglobin in the muscle of the meat - haem can be absorbed directly
Iron can be in the form of ferrous iron (Fe2+) from vegetables - in this instance, the Fe2+ must be converted to the Ferric form (Fe+) i.e. via ferric reductase and this can then be absorbed
SO what are the forms of iron that can be absorbed by the body?
Haem Ferric iron (Fe+)
Why is free flowing iron dangerous and how is this prevented?
Iron can easily accept or donate an electron (hence be easily converted from ferrous to ferric) SO it is dangerous because it can easily oxidise or reduce substances - this can create free radicals
SO the body must prevent the flow of free iron in the blood and hence iron is bound by proteins
What is transferrin and what is it’s role?
Glyco-protein present in blood plasma
Acts as a carrier for iron in the bloodstream
High affinity for iron - can bind two iron atoms at a time (reversible)
How does transferrin transfer iron around the body?
SO transferrin present inside cells and in the blood plasma
A transferrin protein with iron will bind to a transferrin receptor on the surface of a cell e.g. an erythroblast
This complex will then be transported into the cell via endocytosis
Inside the cell, the transferrin release it’s iron ions
The iron is taken up by ferritin and stored for future use
The receptor/transferrin complex is then transported back to the cell surface and the transferrin is released for another round of iron uptake
What happens to iron in the cells once it has been released by transferrin?
The iron ions are then taken up by ferritin and stored for future use
How is iron stored in cells?
Iron stored in the molecule ferritin
Globular protein
Describe the action of ferritin in cells
Ferritin releases iron in a controlled manner
Acts as a buffer agains iron deficiency and iron overload
Plasma ferritin acts as an indirect marker of the total amount of iron stored in the body - can be used as a diagnostic test
Define anaemia and briefly describe it
Low haemoglobin level
Most common blood disorder
Not a diagnosis - a sign of an underlying disorder
What are the normal levels of haemoglobin (NEED TO KNOW)
Male - about 13.5g/dl
Female - about 11.5g/dl
NB. these levels will vary depending on age, sex and race and Hb. levels also decrease with age
What stages should be carried out by a clinician if Hb. levels are low?
History and examination (drugs, family, lymph nodes, weight loss, night sweats)
Full blood count and blood film
Serum B12, colate, ferritin
Test of renal and liver function
Further tests if necessary (Hb. electrophoresis, bone marrow biopsy)
What are the symptoms of anaemia?
Tiredness Fainting Shortness of breath Worsening angina/claudication Rapid heart beat (palpitations)
What are the signs of anaemia?
Pallor Rapid heart rate Bounding pulse Systolic flow murmur Cardiac failure
What are the different potential causes of anaemia?
Decreased production of red blood cells
Increased destruction of red blood cells
Increased loss of red blood cells
What are the different causes of decreased production of red blood cells?
Iron deficiency
B12/folate deficiency
Marrow infiltration e.g. cancer
Chronic disease
Infection
What are the different causes of increased destruction of red blood cells?
Haemolytic anaemia - disorders of RBC membrane/enzyme/haemoglobin
Immune destruction
What is the cause of an increased loss of red blood cells?
Bleeding
How can anaemia be classified into different types?
Inherited or acquired
Macrocytic, microcytic or normocytic
Immune or non-immune (i.e. related to an immune reaction?)
Why can microcytic/macrocytic cells lead to anaemia?
Microcytic - cannot hold enough iron
Macrocytic - take up more space in the capillary and hence block levels of O2 transport
Describe iron-deficiency anaemia
This is a microcytic anaemia - the cells are smaller and are hypochromic as they have lower levels of Hb. i.e. the cells appear less red in colour
Occurs due to a lack of iron in the diet OR due to malabsorption
What factors can enhance iron absorption?
Consumption of haem iron (meat) Ferrous salts Acid pH Iron deficiency Pregnancy - sometimes when iron intake is less, ability to absorb iron is increased Hypoxia
What factors can impair iron absorption?
Consumption of non-haem iron (veg) Ferric salts Alkaline pH Iron overload Inflammatory disorders Drugs - PPIs (protein pump inhibitors)
What are the risk factors for developing iron deficiency?
Age - elderly and premature
Sex - females more than males
Reproduction - menorrhagia (abnormally heavy bleeding and menstruation)
GI - rectal bleeding, change in bowel habit
Drugs - Aspirin (can cause GI bleeding), NSAIDS
Social - diet, esp. vegetarians
Physiological - pregnancy, infancy, adolescence, breastfeeding
How can a clinician confirm a diagnosis of iron deficiency anaemia?
Full blood count - show a low RBC number
Blood film - show microcytic, hypochromic RBCs
Serum ferritin - low
Serum iron total iron binding capacity (TIBC) - low
How can you treat iron deficiency anaemia?
Replace the iron - improve diet, IRON TABLETS (FERROUS SULPHATE), avoid blood transfusion
What are different causes of normocytic anaemia?
Acute blood loss
Bone marrow damage - reduced production of RBCs
Chonic disease - can cause bone marrow damage - can also effect the rate of aging of RBCs
Cancer
Haemolysis (rupture or destruction of erythrocytes)
What are the main microcytic anaemias?
Iron deficiency anaemia
Thalassaemia
