Disorders In Calcium Metabolism Flashcards
What regulates Calcium?
PTH
VitD3
Calcitonin
What state of Calcium do homeostatic mechanisms respond to ?
Ionised
What can cause artefacts in ionised calcium measurements ?
Increases in pH increase protein binding — air, agitation, variation in heparin conc — DECREASE
Lipaemia is increases serum ionised Ca
What should you consider when you see a low total calcium?
Albumin levels
What effect on ions does PTH have?
INCREASE calcium
DECREASE phosphate
What effect on ions does VitD3 have?
INCREASE calcium
INCREASE Phosphate
What should you look at whenever you look at calcium?
PHOSPHATE
ALBUMIN
What happens when you have high calcium and high phosphate?
Produces calcium phosphate which is insoluble and results in irreversible soft tissue calcification.
What clinical signs are associated with hypercalcaemia ?
—PU/PD
—Weakness, lethargy, depression - interferes with neuromuscular transmission
—Inappetence, V+D, Constipation
—facial pruritis and oral discomfort - paraesthesia
— Muscle twitching and fasciculations
—Tachydysrhythmias
— death
How does hypercalcaemia affect renal function?
— interferes with ADH action -> nephrogenic DI
— Impairs NaCl reabsorption in loop - decreases medullary hypertonicity
— if also high phos - Calcium phosphate deposition causes nephron damage
— Vasoconstriction of afferent arterioles -> Reduced GFR and AZOTAEMIA
What clinical pathology is associated with hypercalcaemia?
Hypercalcaemia
+/- phosphate disruption
+/- renal signs - azotaemia and low USG (ICU)
What pathology can cause hypercalcaemia?
Primary hyperparathyroidism
Humoral hypercalcaemia of
malignancy - lymphoma, anal sac adenocarcinoma, multiple myeloma
Non PTH causes
How does the biochem appear in increased PTH Or PTH like activity?
Ionised hypercalcaemia
AND Low or non-elevated phosphate
High PTH-rp measurable for suspect neoplasia
What can cause hypercalcaemia (unrelated to PTH activity)?
Vitamin D toxicity - excessive supplementation - rodenticides, psoriasis creams Granulomatous inflammation HYPOadrenocorticism CKD Grape intoxication Idiopathic Significant osteolysis
What breed/age is predisposed to primary hyperparathyroidism?
Keeshunds
Older dogs - over 6
What can cause primary hyper PT ism?
Functional neoplasm
Other 3 PT glands atrophy
How do primary hyperPT patients present?
Often well - HyperCa may be incidental
Unremarkable PE
May develop urolithiasis and LUT signs - dysuria, pollakiuria, haematuria
How can you distinguish between CKD and hyperPTism ?
CKD - HYPERPHOSPHATAEMIA also present
- fewer patients are actually hyperCa
hyperPT- hypO
What is the most common cause of hypercalcaemia in cats?
How do you diagnose?
Idiopathic
Diagnosis of exclusion
What can occur as a result of idiopathic hypercalcaemia in cats?
Calcium oxalate uroliths throughout UT
How can you manage idiopathic hypercalcaemia?
Diet
IVFT
Furosemide
Bisphosphonates
What is hypercalcaemia more associated in in cats?
CKD
idiopathic
What is hypercalcaemia more associated in in dogs ?
Neoplasia
Primary hyperPT
How can you manage hypocalcaemia?
Give IV calcium gluconate acutely
Give oral calcitriol subacutely
