Minerals

Question 1

what are the main regulators of serum Ca2+ and phosphate concentrations?

Answer 1

• PTH
• vitamin D (calcitriol is active form)
• calcitonin

Question 2

which is actually found in our blood plasma, phosphate or phosphorus?

Answer 2

phosphate, this is what biochem measures!

Question 3

describe PTH’s role in calcium and phosphorus regulation?

Answer 3

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

Question 4

what does vitamin D do?

Answer 4

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

Question 5

what does calcitonin do?

Answer 5

it is secreted in response to HIGH calcium and it inhibits osteoclastic activity and in the kidneys it inhibitis calcium reabsorption

Question 6

calcium exists in 3 forms in circulation which are:

Answer 6

• free ionized (most, and bioactive and hormonally regulated form)
• protein bound (mostly to albumin)
• non protein bound calcium

a biochem mesures total calcium

Question 7

total serum calcium can be affected by _______, which means what?

Answer 7

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

Question 8

can you measure the free ionized form of Ca?

Answer 8

yes, you would do this if you want a more accurate value for calcium in disease states

Question 9

iCa will increase with pathologic disorders involving:

Answer 9

• osteolysis
• decreased renal excretion
• increased GI absorption

Question 10

iCa will decrease with pathologic disorders involving:

Answer 10

• decreased GI absorption
• increased renal excretion
• increased loss in milk/lactation

Question 11

what is the pneumonic for all the causes for a hypercalcemia?

Answer 11

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

Question 12

what is a spurious hypercalcemia?

Answer 12

a fake hypercalcemia, severe lipemia can affect calcium results, so if you’re suspicious, just run the sample again

Question 13

idiopathic hypercalcemia happens in what species?

Answer 13

in young to middle aged cats, some of which have been associated with calcium oxalate uroliths

Question 14

what are some common types of cancer that cause hypercalcemia of malignancy?

Answer 14

lymphoma, apocrine gland adenocarcinoma of the anal sac, and other carcinomas

Question 15

what is PTHrp?

Answer 15

parathyroid related protein, something that neoplasms secrete and it acts just like normal PTH

Question 16

in cases of hypoadrenocorticism, will the hypercalcemia me mild or severe?

Answer 16

mild usually

Question 17

what are some sources of exogenous and endogenous vitamin D (that will cause a hypercalcemia)?

Answer 17

exogenous: rodenticides, human ointments, plants like solanum
endogenous: granulomatous inflammation like with fungi (this is because macrophages produce vitamin D)

Question 18

a hypercalcemia is common to see in renal failure in what species?

Answer 18

horses, they normally excrete excess Ca via the kidneys

Question 19

what is an example of an osteolytic neoplasia?

Answer 19

multiple myleoma

Question 20

what effect does hypercalcemia have on the kidneys?

Answer 20

• 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

Question 21

if the calcium phosphate product is greater than _______, soft tissue mineralization can result causing organ dysfunction

Answer 21

more than 60-80 mg/dL

Question 22

what are the causes of hypocalcemia?

Answer 22

• 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

Question 23

in general, explain what happens with renal secondary hyperparathyroidism?

Answer 23

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

Question 24

why do pregnant, parturient, or lactating animals have a hypocalcemia?

Answer 24

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

Question 25

nutritional hypocalcemia/nutritional secondary hyperparathyroidism is caused by what kind of diets?

Answer 25

diets high in P and low in Ca

Question 26

why does ethylene glycol toxicity cause a hypocalcemia?

Answer 26

metabolites bind to Ca in renal tubules and cause hypercalcuria

Question 27

why is there a hypocalcemia with acute pancreatitis?

Answer 27

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?

Question 28

a low cholesterol can be indicative of what disease process we talked about in one of the cases in class?

Answer 28

protein losing enteropathy

Question 29

which happens in septic/critically ill dogs, cats, and foals, a hyper or hypo calcemia?

Answer 29

a hypocalcemia

Question 30

what is blister beetle toxicity?

Answer 30

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

Question 31

what are some clinical signs you will see with a hypocalcemia?

Answer 31

• increased muscle and neural excitability since threshold for nerve and muscle depol is decreased
• muscle tremors, weakness, ataxia, seizures, etc

Question 32

what are some clinical signs you’ll see with hypercalcemia?

Answer 32

• PUPD (due to affects on ADH), decreased muscle contractility, mineralization/metastatic calcification, altered nervous conduction/excitability

Question 33

what are some reasons for a hyperphosphatemia?

Answer 33

• decreased GFR
• young growing animals
• hypervitaminosis D
• hypoparathyroidism

Question 34

what are some reaons for a hypophosphatemia?

Answer 34

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)

Question 35

what are some reasons for a hypermagnesiemia?

Answer 35

• decreased GFR
• increased administration

Question 36

what are some reasons for hypomagnesiemia?

Answer 36

decreased intake like anorexia, or grass tetany in ruminants

Question 37

what is grass tetany?

Answer 37

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