Minerals Flashcards
what are the main regulators of serum Ca2+ and phosphate concentrations?
- PTH
- vitamin D (calcitriol is active form)
- calcitonin
which is actually found in our blood plasma, phosphate or phosphorus?
phosphate, this is what biochem measures!
describe PTH’s role in calcium and phosphorus regulation?
when blood Ca++ is low in the blood, the parathyroid gland releases PTH, which causes the kidney to icnrease calcium absorption from tubules and increases renal excretion of P, and calcitriol is released from the tubules, which increases intestinal Ca absorption. PTH also causes bone to be resorbed via osteoclasts. This all results in an increase in Ca++ blood levels
what does vitamin D do?
promtes calcium reabsorption in the kidney, promotes absorption of Ca and P from the intestines, and from the bone it promotes release of Ca and P
what does calcitonin do?
it is secreted in response to HIGH calcium and it inhibits osteoclastic activity and in the kidneys it inhibitis calcium reabsorption
calcium exists in 3 forms in circulation which are:
- free ionized (most, and bioactive and hormonally regulated form)
- protein bound (mostly to albumin)
- non protein bound calcium
a biochem mesures total calcium
total serum calcium can be affected by _______, which means what?
hypoalbuminemia
this means if there’s a hypoalbuminemia you can also see a concurrent hypocalcemia, but it only affects the protein bound Ca and not the ionized/free Ca
can you measure the free ionized form of Ca?
yes, you would do this if you want a more accurate value for calcium in disease states
iCa will increase with pathologic disorders involving:
- osteolysis
- decreased renal excretion
- increased GI absorption
iCa will decrease with pathologic disorders involving:
- decreased GI absorption
- increased renal excretion
- increased loss in milk/lactation
what is the pneumonic for all the causes for a hypercalcemia?
H- hyperparathyroidism
A- addisons
R- renal disease/raisins
D- vitamin D (tox or granulomatous dz)
I- idiopathic
O- osteolytic bone lesions
N- neoplastic/hypercalcemia of malignancy
S- spurious/fake
T- temperature/hypothermia
what is a spurious hypercalcemia?
a fake hypercalcemia, severe lipemia can affect calcium results, so if you’re suspicious, just run the sample again
idiopathic hypercalcemia happens in what species?
in young to middle aged cats, some of which have been associated with calcium oxalate uroliths
what are some common types of cancer that cause hypercalcemia of malignancy?
lymphoma, apocrine gland adenocarcinoma of the anal sac, and other carcinomas
what is PTHrp?
parathyroid related protein, something that neoplasms secrete and it acts just like normal PTH
in cases of hypoadrenocorticism, will the hypercalcemia me mild or severe?
mild usually
what are some sources of exogenous and endogenous vitamin D (that will cause a hypercalcemia)?
exogenous: rodenticides, human ointments, plants like solanum
endogenous: granulomatous inflammation like with fungi (this is because macrophages produce vitamin D)
a hypercalcemia is common to see in renal failure in what species?
horses, they normally excrete excess Ca via the kidneys
what is an example of an osteolytic neoplasia?
multiple myleoma
what effect does hypercalcemia have on the kidneys?
- causes renal ischemia and tubular dysfunction
- causes mineralization within the kidney causing ischemia and uroliths if severe
- if goes on for long enough it can cause renal failure
if the calcium phosphate product is greater than _______, soft tissue mineralization can result causing organ dysfunction
more than 60-80 mg/dL
what are the causes of hypocalcemia?
- hypoalbuminemia (protein bound Ca is lost)
- primary hypoparathyroidism (rare, but results in decreased PTH secretion)
- hypovitaminosis D (dietary deficinecy, GI disease and can’t absorb, or chronic renal disease in dogs and cats developing renal secondary hyperparathyroidism
- preganacy/lactating animals
- nutritional deficit
- ethylene glycol tox
- acute pancreatitis
- GI disease in horses
in general, explain what happens with renal secondary hyperparathyroidism?
decreased GFR causes an increase in phosphorus, phosphorus inhibits the enzyme that makes calcitriol, decrease calcitriol synthesis results in low calcium, and low calcium results in excessive PTH production which causes severe bone demineralization
why do pregnant, parturient, or lactating animals have a hypocalcemia?
because Ca and P are being lost in the milk relative to intestinal absorption and bone resorption, usually associated with an increase in PTH with a resistance to PTH or unresponsiveness to target cells
nutritional hypocalcemia/nutritional secondary hyperparathyroidism is caused by what kind of diets?
diets high in P and low in Ca
why does ethylene glycol toxicity cause a hypocalcemia?
metabolites bind to Ca in renal tubules and cause hypercalcuria
why is there a hypocalcemia with acute pancreatitis?
we dont know, think it has to do with glucagon release from an inflamed pancreas which could possibly stimulate calcitonin release which would decease kidney reabsroption?
a low cholesterol can be indicative of what disease process we talked about in one of the cases in class?
protein losing enteropathy
which happens in septic/critically ill dogs, cats, and foals, a hyper or hypo calcemia?
a hypocalcemia
what is blister beetle toxicity?
happens when horses eat blister beetle contaminated alfalfa, causing blisters and irritations in the mouth and in GI tract. it causes a severe hypocalcemia and hypomagnesia
what are some clinical signs you will see with a hypocalcemia?
- increased muscle and neural excitability since threshold for nerve and muscle depol is decreased
- muscle tremors, weakness, ataxia, seizures, etc
what are some clinical signs you’ll see with hypercalcemia?
- PUPD (due to affects on ADH), decreased muscle contractility, mineralization/metastatic calcification, altered nervous conduction/excitability
what are some reasons for a hyperphosphatemia?
- decreased GFR
- young growing animals
- hypervitaminosis D
- hypoparathyroidism
what are some reaons for a hypophosphatemia?
0 mild to moderate decreases are commo and not significant BUT marked decreased are really really bad can due to:
- hemolysis (RBCs need ATP and without it they become more fragile and lyse)
- can cause CNS signs
- ileus
- treament of diabetes mellitus (insulin shifts phosphate into the cells and out of blood)
what are some reasons for a hypermagnesiemia?
- decreased GFR
- increased administration
what are some reasons for hypomagnesiemia?
decreased intake like anorexia, or grass tetany in ruminants
what is grass tetany?
ruminants eating lush grass, decreased Mg uptake by the plants, will causes a very severe decrease in blood Mg, <0.4 and it can cause hypocalcemia too
