Iron deficiency and anaemia of chronic disease Flashcards
What are some iron-containing proteins
Ribonucleotide reductase Cyclo-oxygenase Succinate dehydroenase Cytochrome a,b,c Myoglobin Haemoglobin Catalase Cytochrome P450
Describe the structure of haem
Ring of carbon, hydrogen and nitrogen atoms and in its centre is an iron atom in the ferrous (Fe2+) state.
Haem combines reversibly with oxygen
What is the lifespan of red cells
120 days
How much iron is required a day for production of red cells daily and why
men - 1mg/day
women - 2mg/day
Desquamated cells of skin and gut
Bleeding (menstruation, pathological)
How much iron does a human diet supply and where is it found
12-15mg iron/day
Meat and fish (haem)
Vegetables
Whole grain cereal
Chocolate
Which factors affect iron absorption
Diet - increase in haem iron, ferrous iron
Intestine - acid (duodenum). ligand (meat)
Systemic - iron deficiency, anaemia/hypoxia. pregnancy
Describe how iron is absorbed in the gut
Iron is converted to ferritin in the epithelium of the duodenum and binds to transferrin in the plasma
How does the gut cell alter iron absorption
High iron -> high hepcidin -> low ferroportin (transporter) -> low absorption
What is transferrin
Holds onto iron in the circulation
Has a total iron binding capacity (TIBS)
20-50% of transferrin will be saturated with iron
What stimulates erythropoietin release
- Anaemia
- Tissue hypoxia
- Increase in erythropoietin
- Red cell precursor survive, grow, then differentiate
What is anaemia of chronic disease
Anaemia in patients who are unwell
No bleeding, infiltrated marrow or iron/B12/folate deficiency
What are the lab signs of being ill
C-reactive protein
Erythrocyte Sedimentation Rate
Acute phase response
What is there an increase in during acute phase response
Ferritin
FVII
Fibrinogen
Immunoglobulins
What are some associated conditions with anaemia of chronic disease
Chronic infections e.g. TB/HIV
Chronic inflammation e.g. Rheumatoid arthritis/SLE
Malignancy
Miscellaneous e.g. cardiac failure
Describe the pathogenesis of anaemia of chronic disease
Cytokines prevent the usual flow of iron from the duodenum to red cells
Therefore there is a block in iron utilisation
Cytokines = TNF-alpha and interleukins
What do cytokines do in anaemia of chronic disease
- Stop erythropoietin increasing
- Stop iron flowing out of cells
- Increase production of ferritin
- Increase death of red cells
- Less red cells made
- Iron less available
What are the causes of iron deficiency
Bleeding e.g. menstrual/GI
Increased use e.g. growth/pregnancy
Dietary deficiency e.g. vegetarian
Malabsorption e.g. coeliac
When are full GI investigations done for iron deficiency
Good diet and no coeliac antibodies Male Women over 40 Post-menopausal Scanty menstrual loss
What does a full GI investigation involve
Upper GI endoscopy - oesophagus, stomach, duodenum
Take duodenal biopsy
Colonoscopy
Nothing - small bowel meal and follow through
What are the other investigations done (not full GI) for iron deficiency
Urinary blood loss
Antibodies for coeliac disease
When should nothing be done if a menstruating woman has iron deficiency
<40
Heavy periods of multiple pregnancies
No GI symptoms
What lab parameters are used for investigation of iron deficiency
MCV (mean cell volume) Serum iron Ferritin Transferrin (= total iron binding capacity, TIBC) Transferrin saturation
What are some causes of a low MCV
Iron deficiency
Thalassaemia trait
Anaemia of chronic disease (low or N)
How is a thalassaemia trait confirmed
Haemoglobin electrophoresis to confirm the presence of an additional haemoglobin type
What are the further investigations done for iron deficiency after lab tests
Endoscopy and colonoscopy
Duodenal biopsy
Anti-helicobacter antibodies
Anti-coeliac antiodies
Abdo ultrasound to look at kidneys
Dipstick urine
Pelvic ultrasound to exclude fibroids
What are the classic lab results of iron deficiency
Hb LOW MCV LOW Serum iron LOW Ferritin LOW Transferrin HIGH Transferrin saturation LOW
What are the classic lab results of anaemia of chronic disease
Hb LOW MCV LOW or NORMAL Serum iron LOW Ferritin HIGH or NORMAL Transferrin normal/low Transferrin saturation normal
What are the classic lab results of thalassaemia
Hb LOW MCV LOW Serum iron NORMAL Ferritin NORMAL Transferrin NORMAL Transferrin saturation NORMAL
