Ca, P, Mg Flashcards
1
Q
All calcium in body fluids is ________
A
Ionized
2
Q
Free calcium
A
50%
- free ions
- hormonally regulated and contributes to pathologic states
3
Q
Anion bound calcium
A
Anionic protein
- 40-45%
- negatively charges sites on proteins (mostly albumin)
- changes in blood pH alter binding
4
Q
Nonprotein anion
A
5-10%
- citrates, PO4, lactate, other small, diffusible anions
5
Q
Age
A
- dogs 6-24 weeks of age (1-2 mg/dl higher)
- foals and kittens: same as adults
6
Q
Protein concentration
A
- hypoalbuminemia: decreased bound Ca, thus tCa
7
Q
Intestinal absorption
A
- dogs, cats, cattle: requires vitamin D
- PTH activity augments vitamin D actions to increase absorption
- equines: depends less on vitamin D and more on amount of dietary Ca
8
Q
Bone resorption/deposition
A
- PTH: stimulates Ca pumps in osteocyte –> promote Ca movement from bone to bone fluid to ECF
- vitamin D: enhances Ca resorption from bone by osteoclastic activity and increased response to PTH
- calcitonin blocks osteolysis via direct changes in osteoclasts and reducing activation of progenitor cells
9
Q
Tubular resorption of fCa
A
- fCa and Ca bound to small anions pass freely thru glomerular filtration barrier (protein bound Ca should not pass)
- 66% resorbed passively in proximal tubules
- PTH-regulated by activation of hormone specific adenylate cyclase system
- angiotensin 2 stimulates Na resorption thru the Na/Ca cotransport system (Ca is concurrently resorbed)
10
Q
Ca and PO4 interaction
A
Ca3(PO4) complexes form in healthy animals
- [tCa] x [Pi] in mg/dl > 70 –> metastatic mineralization in tissues occurs
- precipitation may not occur due to inhibitors, or relative amounts of Ca and PO4
11
Q
Increased bone mobilization or intestinal absorption of Ca leads to _______
A
Increased PTH or PTH-related protein
12
Q
Primary hyperparathyroidism
A
Parathyroid adenoma or carcinomas secretion
- hypophosphatemia will be present –> PTH increases renal excretion, but if GFR is decreased PO4 might be normal or increased
13
Q
Hymoral hypercalcemia of malignancy
A
Pseudo-hyperparathyroidism
- PTHrp production in dogs: lymphoma, apocrine gland carcinoma, melanoma
- cats: pulmonary carcinoma, undifferentiated carcinoma, thyroid carcinoma, lymphoma
- horses: myeloma
- some reports of hypercalcemia inducing neoplasms not related to increased PTHrp in dogs, cats, horses
14
Q
Increased vitamin D activity
A
Might have concurrent hyperphosphatemia (intestinal absorption of PO4)
- stimulates formation of Ca binding proteins in intestinal mucosa
- enhances bone resorption (osteolytic cells more responsive to PTH)
- decreases renal excretion
15
Q
Exogenous vs endogenous vitamin D
A
- exogenous: rodenticide, some medicine, plants, dietary intake
- endogenous: granulomatous inflammation, neoplasm-associated hypervitaminosis D
16
Q
Neoplasia in bone
A
Lymphoma and myeloma
- localized bone resorption and corresponding hypercalcemia
- not associated with increased PTH, PTHrp, or vitamin D
17
Q
Acute/chronic renal disease in horses
A
Due to decreased GFR
- lowering dietary Ca intake can reduce or eliminate hypercalcemia
18
Q
Acute/chronic renal disease in cats and dogs
A
- Ca binding to citrate or PO4
- raisin and grape toxicoses
- chronic renal failure in dogs are 10-15% hypercalemic (binding of Ca to retained anions)
19
Q
30% of hypercalcemic dogs have ______
A
Hypoadrenocorticism
- might involve binding to protein or citrate and renal excretion
20
Q
Adrenalectomized dogs
A
Excessive tubular resorption
- increased angiotensin 2 activity –> activates Na/Ca cotransport system
- glucocorticoids: increase renal excretion of Ca (cortisol deficiency may allow more absorption)
21
Q
Increased protein-bound calcium
A
Cases of marked hyperproteinemia associated with multiple myeloma
- increased negatively charged globulins that will bind Ca
- transient decrease in [fCa] –> increase in PTH –> increased [tCa] and [fCa]WRI
22
Q
Other mechanisms of hypercalcemia
A
- IV infusion of Ca
- hemoconcentraiton
- juvenile onset hypothyroidism
- retained fetus and endometriosis
- idiopathic hypercalcemia in cats
23
Q
Hypoalbuminemic hypocalcemia
A
- decreased protein bound Ca
- [fCa] does not decrease, so no clinical signs of hypocalcemia (pseudo-hypocalcemia)
24
Q
Primary hypoparathyroidism
A
Decreased resorption of Ca from bone and/or decreased absorption in the intestine –> hyperphosphatemia is expected (needs PTH to excrete PO4)
25
Pseudo-hypoparathyroidism
Unresponsive PTH receptors/pathways
| - hypocalcemia
26
Hypomagnesemia
Functional hypoparathyroidism state and hypocalcemia
| - adenylate cyclase impaired --> less PTH released and less response to PTH
27
Hypovitaminosis D
Chronic renal disease and failure in dogs, cats, cattle
- abnormal vitamin D metabolism
- protein losing nephropathy in dogs
28
Vitamin D receptor defect
Rickets
- defective receptors and response to vitamin D
- hypocalcemia
29
Exocrine pancreatic insufficiency in dogs
Incomplete digestion of dietary lipids and other ingesta
| - frequently also have hypoalbuminemia that would contribute to hypocalcemia
30
Pregnancy, parturient, lactational
Ca lost to milk or fetal bone development
31
Hypercalcitonsim
Thyroid C neoplasms, reported in older bulls
| - hypocalcemia
32
Nutritional hypocalcemia
Vitamin D deficient diets
| - leads to secondary hyperparathyroidism --> increased bone mobilization (especially in young animals)
33
Oxalate toxicity
Ingestion of plants with high oxalate and low Ca contents
| - horses and ruminants
34
Ethylene glycol toxicity
Excess renal excretion
| - Ca binding to metabolites in renal tubular fluid
35
Metabolic alkalosis
Plasma [HCO3] above the renal threshold --> excretion of Ca with the bicarb
- intravenous HCO3 infusion in cats
36
Furosemide treatment
Inhibition of Na and Cl resorption --> less Ca resorption (depends on Na gradients)
37
Hypocalcemia due to Ca binding with _____
Diffusible anions
| - EDTA, oxalate, citrates
38
Fracture healing
Early stages may contribute to hypocalcemia
39
Acute pancreatitis may cause _____
Hypocalcemia
| - common in dogs and cats
40
Urinary tract obstruction
Mild to moderate hypocalcemia may be present
- may be related to increased [Pi] and binding of fCa
- renal tubular damage resulting in increased renal excretion
41
Phosphate enema
Hyperphosphatemia
- more Ca/PO4 compounds in plasma and complexes in tissues
- increased excretion of PO4 and consequently Ca
42
GI disorders in horses causes ______
Hypocalcemia
43
Myopathies
Hypocalcemia may occur in several equine myopathies
44
Acute tumor lysis syndrome
Released PO4 may form complexes and deposits with Ca and bind and inhibit Ca tubular resorption
45
Rumen overload and hyperadrenocorticism in dogs also cause _____
Hypocalcemia
46
[fCa] is tightly controlled by _____
Hormones
- abnormal Ca regulation --> clinical signs
- [tCa] often parallels [fCa] but not always
47
Hypocalcemia caused by hypoproteinemia or hypoalbuminemia
[tCa] decreased (less protein-bound Ca)
| - [fCa] may be WRI
48
Hypercalcemia in renal failure or multiple myeloma
[tCa] increased (more bound Ca with abnormal globulin, citrate, or PO4}
- [fCa] may be WRI
49
Hypocalcemia in urinary obstruction in cats
Decreases in [fCa] may be greater and more common than decreases in [tCa]
- Ca may be bound to PO4 and other anions that are not excreted
50
Chronic renal failure in dogs
55% had decreased total or free Ca, 33% had increased
| - changes in [tCa] did not correlate to changes in [fCa]
51
Hyperthyriodism in cats
Decreased [fCa]
| - [tCa] WRI
52
Endurance sports in horses
Decreased [fCa]
| - [tCa] WRI
53
Blood transfusion
Massive transfusion of blood or plasma containing citrate as anticoagulant can cause decreased [fCa]
54
Acidotic calves (due to diarrhea)
Both were decreased, but [tCa] was decreased more
- both decreased after fluid therapy
- therapy with NaHCO3 can rapidly decrease the [fCa]
55
Change in blood pH affects binding to proteins and other anions
- acidemia --> less binding --> increases [fCa]
| - alkalemia --> more binding --> decreases [fCa]
56
Organic acidosis
Changes depend on severity and duration
- lactate or acetoacetate may bind Ca --> decreases [fCa]
- if present in tubular fluid, decrease resorption
- if acidemia also present --> increases [fCa]
57
Blood pH also affects [PTH]
Increased in experimental acidoses, decreased in alkaloses
58
Routine assays measure
[tCa]
- free
- protein bound
- bound to anions other than proteins
59
Serum [fCa] values might be inaccurate when _______
Blood not handled properly
- anaerobically
- separate serum from clot immediately
- no use of serum separator tubes
60
Hypocalcemia values
Decreased protein/albumin = decreased bound
| - normal [fCa] regulation: WRI
61
Hypocalcemia with normal protein concentrations
Low [tCa] indicates decreased [fCa]
- inadequate PTH or vitamin D activties
- bound Ca is unchanged
62
Severity of decreased [fCa] may not be evident from [tCa] if bound Ca is _____
Increased
- chronic renal failure: abnormal vitamin D metabolism --> decreased [fCa]
- increased citrate and PO4 --> increased [bound Ca]
63
Hypocalcemia due to in vitro changes
Excess heparin in sample can cause falsely decreased [fCa]
| - binding to heparin
64
Hypercalcemic samples usually have high _____
[fCa]
- PTH, PTHrp, vitamin D activities increased
- bound Ca might be unchanged
65
WRI [tCa]
Normocalcemia and hypoproteinemia
| - suggests increased [fCa]
66
[fCa] is affected by altered _______
Plasma pH and nonprotein anions
- lactic acidosis -->
- acidemia: decreases protein-bound
- nonprotein anions: increased [bound Ca]
67
Different forms of phosphorous
- pH 7.4: H2PO4 and HPO4 are in a 1:4 ratio
- 10% bound to cationic proteins
- 35% bound to nonprotein cations
- 55% is free
68
Renal clearance of PO4
Major route of excretion
| - PTH is potent phosphaturic agent (inhibit resorption in distal tubules)
69
Absorption of PO4 in intestines
Enhanced by 1,25 DHCC (calcitriol, metabolite of vitamin D)
70
Resorption from bone
PTH stimulates osteocytes and osteoclasts to release PO4 from bone
71
Shifting of PO4 between ICF and ECF
Insulin promotes entry into cells
72
Animal age
- growth hormone: increases renal resorption --> increased [Pi]
- serum [Pi] is greater in young, growing animals than in the adult
73
Decreased urinary PO4 excretion
- decreased GFR: magnitude parallels severity in most species except horses
- urinary bladder rupture or urine leakage into tissues
- decreased [iPTH] or activity: primary or pseudo hypoparathyroidism
- acromegaly: growth hormone increases tubular PO4 resorption
74
Increased PO4 absorption from intestine
- phosphate enema or ingestion of phosphate urinary acidifier
- increased vitamin D
- intestinal lesions: devitalized intestinal mucosa allows PO4 to enter plasma
- diets with low Ca:PO4 ratio
75
Shift from ICF to ECF
Myopathies (release from damaged muscle fibers)
| - acute tumor lysis syndrome: release from necrotic neoplastic cells
76
Pseudo-hyperphosphatemia
In cases of hyperbilirubinemia, monoclonal gammopathy, in vitro hyemolysis
77
Other mechanisms of hyperphosphatemia
- hyperthyroidism in cats
- lactic acidosis
- hyperadrenocorticisim in dogs
78
Increased urinary excretion
- prolonged diuresis: less PO4 is resorbed
- increased PTH or PTHrp
- fanconi syndrome: proximal tubular defect --> decreased resorption of glucose, amino acids, and PO4
79
Decreased intestinal PO4 absorption
- prolonged anorexia or PO4 deficient diet
- PO4 binding agents
- hypovitaminosis D
- intestinal malabsorption
80
Shift of PO4 from ECF to ICF
- hyperinsulinism: promotes entry into cells
- glucose infusion
- solute diuresis and increased insulin
- respiratory alkalosis
- PO4 into erythrocytes, due to increased phosphorylation during accelerated glcolysis
81
Defective mobilization of PO4 from bone
- postparturient paresis (milk fever) and eclampsie
| - inability to mobilize sufficient Ca and PO4 from bones to replace what is lost in milk
82
Equine renal disease
May be seen in hypercalcemic cases, not a consistent finding
- halothane anesthesia in horses
- hypophosphatemia
83
Pseudo hypophosphatemia due to conjugated
Hyperbilirubinemia
