Lecture 14: Absorption Flashcards

Question

What is megaloblastic anaemia?

Answer 1

Impaired maturation of red blood cells, leading to the production of abnormally large and immature cells. It is primarily caused by a deficiency of either vitamin B12 or folate (vitamin B9), which are essential for DNA synthesis and red blood cell production.

Answer 2

autoimmune response that targets and destroys the gastric parietal cells in the stomach, which are responsible for producing intrinsic factor—a protein required for the absorption of vitamin B12.

Answer 3

- Inadequate dietary intake - Loss of gastric parietal cells or intrinsic factor - Functionally abnormal intrinsic factor - Bacterial overgrowth in intestine eg stagnant loop syndrome - Disorders of ileal mucosa eg resection, absence of receptor on ileal cells -Disorders of plasma transport eg transcobalamin II deficiency -Dysfunctional uptake and use of vitamin B12 by cells

Answer 4

- PPI and H2 antagonists - Oral contraceptives - Metformin - Cholchicine

Answer 5

Stomach acid helps to seperate B12 from food, a reduction in stomach acid, reduces the separation of B12 from food

Answer 6

thought to be due to a reduction in the B12 carrier transcobalamin

Answer 7

Metformin interferes with B12 absorption

Answer 8

impairs or inhibits receptors in terminal ileum.

Answer 9

- Megaloblastic anaemia - Parasthesia in hands and feet - Sensory loss - Gait ataxia - Weakness in legs - Subacute combined degeneration (SCD) of the spinal cord - Hunters glossitis - Angina - Venous thromboembolic disease - Infertility

Answer 10

- cyanocobalamin - hydroxycobalamin - deoxyadenosylcobalamin - methylcobalamin

Answer 11

- Deoxyadenosylcobalamin - methylcobalamin

Answer 12

- Oral cobalamin: cyanacobalamin - Parenteral cobalamin: hydroxycobalamin

Answer 13

in the case of gastric intrinsic factor deficiency (pernicious anaemia) or total gastrectomy.

Answer 14

Dark green vegetables eg broccoli, lettuce, Brussel sprouts and spinach, dried legumes eg beans lentils and chickpeas. Fruit and fruit juices. Meat, seafood, poultry and eggs. Fortified cereal and bread.

Answer 15

200 micrograms a day, 400 in pregnancy

Answer 16

- In the diet folate exists in a polyglutamate form, which needs to be converted to a monoglutamate form for absorption - Natural folate are conjugates to a polyglutamyl chain. - During digestion, the polyglutamate form of dietary folate is broken down into monoglutamates by enzymes in the small intestine, this mainly occurs in the duodeum and jejunum - The monoglutamate forms of folate are then transported across the intestinal cells through an active transport mechanism. This process requires specific carrier proteins located on the brush border of the intestinal cells. Hydrolysed by folylpoly-g-glutamate carboxypeptidase. - Once inside the intestinal cells, folate is converted into its active form, called 5-methyltetrahydrofolate (5-MTHF). This conversion is facilitated by enzymes in the intestinal cells.

Answer 17

- Inadequate dietary intake - congenital defects in the uptake system eg Proton coupled transported - intestinal disease eg coeliac disease, IBD, tropical sprue - drug interaction e.g. cholestyramine, sulfasalazine, trimethoprim, methotrexate, metformin) - Chronic alcohol use - increased cellular requirement (e.g. pregnancy)

Answer 18

- Sore tongue (glossitis) and pain upon swallowing, GI symptoms (nausea, vomiting, abdominal pain diarrhoea, especially after meals), Neurologic (cognitive impairment, dementia, and depression), When severe it results in megaloblastic anaemia.

Answer 19

* Oral folic acid for 1-4 months * Oral route is sufficient even in those with malabsorption * Treated until haematological recovery occurs