Lecture 18 11/12/24

Question 1

What is a serum iron test?

Answer 1

test that evaluates iron in circulation bound to transferrin

Question 2

What is a total iron binding capacity test?

Answer 2

test that evaluates plasma’s capacity to carry iron

Question 3

What is a % saturation test?

Answer 3

calculated result that indicates what % of transferrin molecules are bound by iron

Question 4

What is a ferritin test?

Answer 4

immunoassay that quantifies plasma ferritin concentrations and correlates to total body stores

Question 5

What is a bone marrow iron test?

Answer 5

visual qualitative assessment of hemosiderin stored in marrow macrophages

Question 6

Which test is considered “gold standard” for assessing total body iron stores?

Answer 6

bone marrow iron

Question 7

What are the characteristics of absolute iron deficiency?

Answer 7

-decreased total body stores of iron
-occurs through chronic external blood loss

Question 8

Why is it difficult to correct absolute iron deficiency with oral replacement therapy?

Answer 8

only a small amount of iron is absorbed from the GI tract in veterinary species

Question 9

What are the characteristics of anemia of inflammatory disease?

Answer 9

-hepcidin binds to ferroportin and causes its internalization and degradation
-reduced export of dietary iron into circulation
-sequestration of storage forms of iron occurs in macrophages

Question 10

How does absolute iron deficiency present on different iron tests?

Answer 10

-decreased serum iron
-normal to increased total iron binding capacity
-decreased % saturation
-decreased ferritin
-decreased bone marrow iron

Question 11

How does functional iron deficiency/inflammatory iron deficiency present on different iron tests?

Answer 11

-decreased serum iron
-normal to decreased total iron binding capacity
-normal to decreased % saturation
-increased ferritin
-increased bone marrow iron

Question 12

What are the characteristics of hepatic insufficiency and portosystemic shunts?

Answer 12

-approximately 50% of dogs with PSS have low serum iron and decreased total iron binding capacity
-mechanism is unknown but presumed to be iron sequestration
-ferritin is normal to increased

Question 13

What can lead to an iron overload?

Answer 13

-hemolytic disease**
-chronic blood transfusions
-excess dietary or parenteral iron administration

Question 14

Where is PTH sourced from?

Answer 14

parathyroid gland

Question 15

What are the target organs of PTH?

Answer 15

-bone
-kidney
-intestine

Question 16

What is the net hormone effect of PTH on plasma conc.?

Answer 16

-increased calcium
-decreased phosphate

Question 17

Where is vitamin D sourced from?

Answer 17

-GI absorption
-skin metabolism

Question 18

What are the target organs of vitamin D?

Answer 18

-bone
-kidney
-intestine

Question 19

What is the net hormone effect of vitamin D on plasma conc.?

Answer 19

-increased calcium
-increased phosphate

Question 20

Where is calcitonin sourced from?

Answer 20

C-cells of the thyroid gland

Question 21

What are the target organs of calcitonin?

Answer 21

-bone
-kidney
-intestine

Question 22

What is the net hormone effect of calcitonin on plasma conc.?

Answer 22

-decreased calcium
-decreased phosphate

Question 23

Where is FGF23-Klotho sourced from?

Answer 23

bone

Question 24

What is the target organ of FGF23-Klotho?

Answer 24

kidney

Question 25

What is the net hormone effect of FGF23-Klotho on plasma conc.?

Answer 25

decreased phosphate

Question 26

What are the characteristics of free/unbound Ca2+?

Answer 26

-ionized calcium -physiologically active fraction -regulated fraction in health -contributes to pathologic states

Question 27

What are the characteristics of protein-bound Ca2+?

Answer 27

-80% bound to albumin -20% bound to globulins -acts as a storage/buffer pool -influenced by body pH

Question 28

What are the characteristics of complexed Ca2+?

Answer 28

-bound to non-protein anions -anions include citrate, lactate, and phosphate

Question 29

Which factors affect plasma Ca2+?

Answer 29

-young age -body protein status -intestinal absorption -resorption from bones -urinary excretion

Question 30

Which hormones affect plasma Ca2+, and in which direction?

Answer 30

-PTH; increase -vitamin D; increase -calcitonin; decrease

Question 31

What are the causes of hypercalcemia?

Answer 31

-hyperparathyroidism -osteolysis -granulomatous disease -spurious/analytical error -idiopathic -neoplasia -young animals -Addison's disease -renal failure -vitamin D excess

Question 32

What are the characteristics of primary hyperparathyroidism?

Answer 32

-occurs due to hyperplasia or neoplasia of parathyroid glands -increased fCa2+ -increased or within reference interval PTH

Question 33

What are the characteristics of hypercalcemia of malignancy?

Answer 33

-PTH related protein (PTHrp) behaves like PTH and has similar biologic effects -PTHrp is secreted by neoplasms such as T cell lymphoma or apocrine gland of the anal sac carcinoma

Question 34

How does hypoproteinemia lead to hypocalcemia?

Answer 34

-fCa2+ is tightly regulated by hormones -if protein decreases, calcium is excreted by kidneys or removed to storage pools; it does not shift to fCa2+

Question 35

What are the characteristics of direct fCa2+ measurement?

Answer 35

-done on blood gas instrument -use heparinized whole blood -maintain anaerobic conditions -measure sample right away

Question 36

What are the characteristics of primary hypoparathyroidism?

Answer 36

-due to low production of PTH -low fCa2+ -low or within lower reference interval PTH -increased or within upper reference interval PO4 -uncommon in vet med

Question 37

What are the characteristics of hypovitaminosis D/secondary hyperparathyroidism?

Answer 37

-most commonly occurs in CKD patients -can be seen with nutritional deficiency or chronic GI disease -low or within lower reference interval fCa2+ -PTH increased or within upper reference interval

Question 38

What are the characteristics of total calcium measurement?

Answer 38

-done on chem. analyzer -serum or heparinized plasma sample -avoid EDTA and citrate anticoagulants

Question 39

What are the fractions of PO4?

Answer 39

-free; 55% -protein-bound; 10% -complexed; 35%

Question 40

What are the factors that affect plasma PO4?

Answer 40

-young age -intestinal absorption -resorption from bones -urinary excretion -shifting between compartments

Question 41

Which hormones affect plasma PO4, and in which direction?

Answer 41

-PTH; decrease -vitamin D; increase -calcitonin; decrease -FGF23-Klotho; decrease

Question 42

What are the characteristics of phosphate measurement?

Answer 42

-done on chem. analyzer -serum or heparinized plasma sample -avoid hemolysis; RBCs contain phosphate, can artifactually increase readout

Question 43

Why is it important to evaluate calcium and phosphate together?

Answer 43

-sustained hypercalcemia can result in metastatic calcification -[Ca2+]x[PO4] greater than 70 indicates increased risk of metastatic dysfunction -concern for renal dysfunction

Question 44

What are the characteristics of magnesium?

Answer 44

-majority of Mg2+ is intracellular -1-2% of Mg2+ is in plasma -fMg2+ is the active fraction

Question 45

What is the breakdown of Mg2+ plasma distribution?

Answer 45

-55-60% fMg2+ -30-40% protein-bound Mg2+ -4-6% complexed Mg2+

Question 46

What factors affect plasma Mg2+?

Answer 46

-body protein status -intestinal absorption -urinary excretion -shifting between compartments

Question 47

Which hormones impact plasma Mg2+, and in which direction?

Answer 47

-PTH; increased -aldosterone; decreased -thyroxine; decreased

Question 48

What are the characteristics of total magnesium measurement?

Answer 48

-done on chem. analyzer -serum or heparinized plasma sample -avoid EDTA and citrate anticoagulants

Question 49

What are the characteristics of free magnesium measurement?

Answer 49

-done on blood gas instrument -heparinized whole blood sample -quick, anaerobic handling -measure sample as soon as possible