Plasma proteins and calcium Flashcards
(27 cards)
Size of albumin
60-65KDa
What is the half life of albumin in dogs?
8 days - then increases as the size of the animal increases so 2-3wks in cattle
What types of proteins make up the group of globulins?
Acute phase proteins
Lipoproteins
Anti-inflammatory proteins
Immunoglobulins
Main function of plasma proteins
Maintenance of colloid osmotic pressure
Causes of selective hypoalbuminaemia
Decreased albumin production
Increased selective abumin losses
Causes of decreased albumin production
Systemic inflammation - usually mild, often with increased globulins
Marked hepatocellular dysfunction - mild to marked, globulins may be increased, also would see markers of liver dysfunction
Intestinal malabsorption - mild to marked, globulin usually normal
Causes of increased selective albumin losses
Protein losing nephropathy - secondary to renal glomerular damage - mild to marked - normal gobulins, marked proteinuria, often hypercholesterolaemia, can be azotaemic
Causes of selective hypoglobulinaemia
Uncommon
Neonatal animals secondary to FPT - use zinc turbidity test, measure serum GGT, or serum TP
Causes of non-selective hypoproteinaemia
Haemorrhage - also see anaemia (unless in first 24hrs)
Protein losing enteropathy (PLE) - due to generalised SI disease or lymphatic obstruction, see diarrhoea, may also have hypercholesterolaemia
Third space losses - secondary to inflammation of pleura, peritoneum, or vasculature (increased permeability of vessel walls), see peripheral oedema or body cavity effusions
Causes of hyperglobulinaemia with normal/low serum albumin
Systemic inflammation (polyclonal gammopathy) - will also see SAA increase
Aberrant immunoglobulin production secondary to B lymphocyte or plasma cell neoplasia (monoclonal gammopathy)
Acute phase proteins
Proteins that change concentration in response to systemic inflammation.
Increase within 24hrs of onset
E.g SAA, CRP, fibrinogen (in large animals)
Causes of hyperalbuminaemia with normal/low serum globulin concentration
Rare, can be associated with steroid therapy (stimulate increased production)
Causes of non-selective hyperproteinaemia
Usually associated with haemoconcentration secondary to dehydration. Will have other signs of dehydration clinically and on bloods.
Calcium regulation
Decreased ionised calcium detected by the parathyroid glands
Increased parathyroid hormone (PTH) production
-> reabsorption of calcium from urine
-> Increased calcitriol (activated vitamin D) production in the kidney -> increased absorption of calcium from intestine
-> increased resorption of calcium from the bone
Ionised calcium back to homeostatic point
Calcium in the blood (what formations?)
50% is free (ionised calcium)
40-45% is bound to proteins (mostly albumin)
5-10% is complexed to other anionic compounds (e.g. phosphate)
What is ionised hypercalcaemia associated with? (signs)
PUPD - because calcium inhibits ADH activity
GI signs - vomiting, diarrhoea, anorexia
Metastatic calcification and damage to organs
What is ionised hypocalcaemia associated with? (signs)
Muscle twitching and weakness
(neurological signs)
Measurement of blood calcium
Total calcium - cheap and easy, fairly specific to ionised hypercalcaemia but not at all sensitive, not specific if showing hypocalcaemia.
Ionised calcium - care needed with sample (can’t be exposed to air), ideally should be measured patient side
Causes of pseudohypercalcaemia
Hyperphosphataemia e.g. CKD (phosphate binds to calcium)
Hyperalbuminaemia/marked hyperglobinaemia (e.g. multiple myeloma or haemoconcentration)
Causes of ionised/free hypercalcaemia
Increased PTH production due to primary hyperparathyroidism (tumour)
Increased parathyroid hormone related peptide (PTHrP) production (paraneoplastic)
Hypervitaminosis D
Osteolytic lesions
Hypoadrenocorticism
Renal diet associated
Idiopathic in cats
What other changes are you likely to see with primary hyperparathyroidism
Ionised hypercalcaemia
Low or low-normal serum phosphate (PTH enhances renal excretion)
Secondary hyperparathyroidism
E.g. renal or nutritional
Not associated with hypercalcaemia as there is still appropriate homeostatic compensation for hypocalcaemia
Most common neoplasia causing paraneoplastic hypercalcaemia
Lymphoma, multiple myeloma, anal sac adenocarcinoma
Investingating ionised hypercalcaemia
Exclude lymphoma (LN palpation) and AGASAC (rectal palpation) and aspirate any enlrged LNs or masses.
Imaging to identify internal masses.
Hypoadrenocorticism can be excluded by basal cortisol measurement
Radiographs of bones to look for osteolytic lesions
Refer for specialised testing: US of parathyroids, measurement of serum PTH and PTHrP, measurement of serum vitamin D
