Haem 9 - Iron deficiency Flashcards
List some compounds containing iron
Haemoglobin - most of the iron is in Hb Myoglobin Catalase Cytochrome P450 Ribonucleotide reductase Cyclo-oxygenase Cytochrome a,b,c Succinate dehydrogenase
What is the role of iron in Hb?
Holds onto oxygen. Ferrous iron sits in the centre of protoporphyrin ring.
low iron = low Hb = anaemia
What is the daily requirement of iron? Describe the absorption of iron.
20mg iron/day - fortunately iron is recycled
Human diet provides 12-15 mg iron/day in most foods: meat and fish (haem), vegetables and whole grain cereal. However most iron is not absorbed.
Only Fe2+ is absorbed.z
How is iron lost from the body?
1) Desquamated cells of skin and gut (shedding off of cells)
2) Bleeding - menstruation
To replace these losses in iron:
Men require: 1mg/day
Women require: 2mg/day
What are the factors that affect the absorption of iron?
DIET: increase in haem iron (red meat+fish)
- ferrous iron (you can absorb)
INTESTINE: acid (duodenum)
- ligand (meat)
SYSTEMIC: iron deficiency (you absorb more iron)
- anaemia/hypoxia
- pregnancy
How does the gut cell alter iron absorption?
Iron is transported across the basal side side of the cell by ferroportin. Ferroportin is regulated by hepcidin - high levels of hepcidin causes ferroportin to be internalised = decreased iron transport.
High iron –> High hepcidin –> Low ferroportin –> Low absorption
What forms can iron exist in?
Iron absorbed in the diet
Ferritin = intracellular iron
Iron is attached to transferrin = plasma iron
Describe transferrin
Binds to iron in the circulation:
Transferrin saturation
- usually 20-40% saturated with iron
- low iron would show low transferrin saturation
TIBC - Total Iron Binding Capacity
What are the three effects of erythropoietin?
Causes erythrocytes to:
- Survive
- Grow
- Differentiate
Define anaemia of chronic disease
ACD: Anaemia in patients who are unwell but there is no obvious cause except that they are ill
What are the laboratory signs that a patient is ill causing ACD?
C-reactive protein - mark of infection/inflammation
Erythrocyte Sedimentation Rate - ESR goes up in inflammation
Acute phase response- increases in
- ferritin
- FVIII
- fibrinogen
- immunoglobulins
What the common associated conditions of ACD?
Chronic infections e.g. TB/HIV
Chronic inflammation e.g. RhA/SLE
Malignancy
Miscellaneous e.g. cardiac failure
Describe the pathogenesis of ACD?
Cytokines released prevent the usual flow of iron from the duodenum to red cells - essentially blocks iron being utilised.
Examples of cytokines - TNF alpha and Interleukins
- Stop erythropoietin increasing
- Stop iron flowing out of cells
- Increase production of ferritin
- Increase death of red cells
Therefore - make less red cells - more red cells die - less availability of iron (stuck in cells/ferritin)
What are the causes of iron deficiency?
- Bleeding e.g. menstrual/GI
- Increased use e.g. growth (puberty children growing quickly)/pregnancy (baby with take the iron first)
- Dietary deficiency e.g. vegetarian because they don’t get haem in meat and fish
- Malabsorption e.g. coeliac - affect absorption of iron
When are full GI investigations performed?
Iron deficiency is taken seriously if you are iron deficient and anaemic.
- Good diet and no coeliac antibodies…..
- Male
- Women over 40
- Post menopausal women
- Women with scanty menstrual loss
You want to exclude coeliac disease, colon cancer and gastric cancer - this is to ensure there is no GI bleeding.
Menstruating woman <40 ….if heavy periods OR multiple pregnancies and no GI symptoms do nothing. These are all reasons for why there is anaemia so you don’t need to look at the GI tract.
What are full GI investigations?
Upper GI endoscopy - oesophagus, stomach, duodenum
Take duodenal biopsy
Colonoscopy
Remember you’re trying to ensure there is no colon or gastric cancer.
IF FIND NOTHING
- small bowel meal and follow through
Other investigations include:
Urinary blood loss - this may be due to kidney cancer. Any leak of blood over period of time will result in anaemia.
Antibodies for coeliac disease
What are the laboratory investigations for iron deficiency?
MCV (mean cell volume) Serum iron Ferritin Transferrin (= total iron binding capacity, TIBC) Transferrin saturation
What are the causes of low MCV? Describe the level of serum iron.
Iron deficiency - low serum iron
Thalassaemia trait - normal iron
Anaemia of chronic diseases (low or normal MCV) - low serum iron because because in ACD the flow of iron is being blocked.
How do you confirm thalassaemia trait?
- Haemoglobin electrophoresis
- Confirms an additional type of haemoglobin is present
Describe the levels serum ferritin
Good test for iron deficiency
Low in iron deficiency (HELPFUL)
Normal = doesn’t completely exclude iron deficiency (more than one disease, raised CRP or ESR) + Chronic disease
High in Chronic disease
Ferritin is supposed to be in cells but will leak into the blood. Very reflective of iron stores if it is low. However ferritin levels can be affected if the patient has more than one disease. e.g Iron deficient but also chronic disease. RhA(ACD) plus bleeding ulcer (iron deficient).
Low ferritin suggests iron deficiency –> upper and low GI endoscopy to look for bleeding.
Describe how the levels of transferrin and transferrin saturation can vary?
Iron deficient: transferrin goes up + low saturation
Chronic disease: Normal or even low + normal saturation
Describe the laboratory results from classic iron deficiency
Hb - LOW MCV - LOW Serum Iron - LOW Ferritin - LOW Transferrin saturation - LOW
Transferrin - HIGH
Describe the laboratory results from anaemia of chronic disease
Hb - LOW MCV - LOW or normal Serum Iron - LOW Ferritin - HIGH or normal Transferrin - NORMAL/LOW Transferrin saturation - NORMAL
Describe the laboratory results for thalassaemia?
Hb - LOW MCV - LOW Serum Iron - NORMAL Ferritin - NORMAL Transferrin - NORMAL Transferrin saturation - NORMAL
