DS: B12 Deficiency Flashcards

4406888674	What is the structure of B12?	Corrinoid ring (made of 4 pyrrole rings)	0
4406890722	What does B12 convert homocysteine to?	Removes and keeps a methyl group converting it to methionine	1
4406891975	What is B12 involved in?	DNA synthesis Neurotransmitter regulation	2
4406892857	What are the dietary sources of B12?	- Made by bacteria; found in cow products, meat, shellfish, eggs, milk - Added to fortified grain products (cereals)	3
4406894473	What is the RDI of B12?	2.4 ug/day	4
4406894836	Why is the RDI for B12 so low?	The body is very good at conserving B12 and it is stored in the liver	5
4406895641	What is the first step for the absorption of B12?	- Foods containing B12 enter the stomach - In the fundus HCl and pepsin break up proteins to release food trapped cobalamin - Hepatoccrin complexes with B12 and travels to the duodenum	6
4406899003	What occurs in the duodenum during B12 absorption?	Pancreatic proteases degrade HC.Cbl and releases B12 B12 then binds to IF to be absorbed	7
4406900667	What occurs in the terminal ileum during B12 absorption?	IF.Cbl is absorbed in the terminal ileum via the brush border - IF receptors on enterocytes - Inside the enterocytes Cbl. is released from IF	8
4406903223	What is Cbl converted to and used for in enterocytes?	- 20% converted to holotranscobalamin (TC.Cbl) and taken up by all cells for DNA synthesis, it has a short half life - 80% is conjucgated with hepatocorrin and transported to the liver for storage	9
4406907816	How is recycled B12 used?	Released in the bile (1mg) - most is reabsorbed (associated with IF) into the enterohepatic circulation - The liver is capable of storing several years worth of B12	10
4406909926	What type of anaemia is most commonly associated with B12 deficiency?	Megaloblastic macrocytic pernicious anaemia	11
4406911032	What symptom is seen with B12 but not folate deficiency?	Neuropathy - sub acute combined degeneration of spinal cord - Possible caused by a build up of SAM	12
4406912235	What patients require B12 supplementation?	- Vegans - Malabsorption syndromes e..g pernicious anaemia	13
4406913793	What is the normal Hb range?	125-170 g/L	14
4406914351	What is the normal MCV range?	80-100 fL	15
4406915070	What is the normal range for a platelet count?	150-400	16
4406915288	What is the normal range for reticulocytes?	10-100	17
4406916027	What type of cells are present in megaloblastic anaemia?	Hypersegmented neutrophils	18
4406916776	How does the bone marrow usually respond to the stimulus of anaemia?	By increasing reticulocyte numbers	19
4406920071	What are characteristics of macrocytic megaloblastic anaemia?	Low Hb High MCV Hypersegmented neutrophils	20
4406920900	What are low reticulocyte numbers usually a sign of?	Impaired bone marrow production (erythropoiesis)	21
4406921914	What are the requirements for normal erythropoiesis?	Iron Folate B12	22
4406922634	What other symptoms, besides anaemia, would B12 deficiency be associated with?	Loss of concentration Tingling in fingers	23
4406923097	What are some causes of low B12?	- Diet - veg/vegans - Failure of absorption	24
4406924040	What are some causes of failure of absorption of B12?	- Small intestine problems; B12 binds IF but not absorbed in SI (surgery to remove terminal ileum or antrum), Crohn's disease - Stomach problems; no IF e.g. pernicious anaemia	25
4406927697	What are the requirements for the normal absorption of B12?	- Acid to release food bound cobalamin - Secretion of IF from healthy parietal cells - Normal pancreatic secretion - Normal ileal function	26
4406934873	What does Shillings test measure?	The amount of oral B12 that is actually absorbed with IF	27
4406935857	What is a normal amount of B12 to be excreted in a Shilling's test?	>10% of the oral dose	28
4406937098	If the B12 absorption can be normalised with a dose of IF what is the likely cause?	Pernicious anaemia/gastritis If not corrected with IF the problem is with the distal ileum	29
4406938358	What are some disadvantages of Shilling's test?	Time consuming, requires radio-isotopes and collection of urine Results are difficult to interpret- distinction between ileal and gastric disease is not clear cut	30
4406940322	How can you look for evidence of autoimmune gastritis?	- Antibodies to parietal cells (also present in healthy individuals) - Antibodies to IF (Specific but not sensitive) - Other auto-immune diseases (thyroid) - Gastric biopsy - Low acid output with high plasma gastrin levels	31
4406942646	How is B12 deficiency treated?	B12 replacement - Depleted reserves that have taken 3-5 years to run out - Need high doses to replace - 1000 ug every week for 4-6 weeks then maintenance of 1000 ug every 3 months (IM) - Monitor to response to B12 replacement	32
4406949467	What symptoms should improve with B12 replacement therapy?	- Weight loss and diarrhoea improved after 1-2 months - Small bowel is actively replicating tissue that requires B12 to maintain cell turnover - Overall integrity and health of small bowel mucosa improves - normal function	33
4406951915	What type of anaemia is iron deficiency associated with?	Microcytosis anaemia	34
4406952777	How does a terminal ileal resection cause low B12?	Loss of specialized receptors on terminal ileum which leads to; - Failure to absorb B12 - Failure to reabsorb bile salts which cause irritation on colon (secretary diarrhoea) and impaired absorption of fat	35
4406955313	What is involved in a Bilroth I distal gastrectomy?	Distal antrum and beginning of duodenum removed with ends rejoined	36
4406956342	What is involved in a Bilroth II distal gastrectomy?	Distal antrum and beginning of duodenum removed. Duodenum sealed and jejunum sewed onto stomach	37
4406957708	How does a partial gastrectomy cause low B12?	- Loss of gastric acid secretion - Atrophic gastritis due to bile reflux due to absence of pylorus - Failure of normal stimulation on pancreatic secretion/failure of mixing of pancreatic juice with food	38
4406960738	How does Coeliac disease cause low B12?	- Loss of small bowel villi - Loss of endocrine cells that secrete secretin and cholescystokinin	39