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Clinical Pathology > Ca, P, Mg > Flashcards

Ca, P, Mg Flashcards

1
Q

All calcium in body fluids is ________

A

Ionized

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2
Q

Free calcium

A

50%

  • free ions
  • hormonally regulated and contributes to pathologic states
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3
Q

Anion bound calcium

A

Anionic protein

  • 40-45%
  • negatively charges sites on proteins (mostly albumin)
  • changes in blood pH alter binding
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4
Q

Nonprotein anion

A

5-10%

- citrates, PO4, lactate, other small, diffusible anions

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5
Q

Age

A
  • dogs 6-24 weeks of age (1-2 mg/dl higher)

- foals and kittens: same as adults

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6
Q

Protein concentration

A
  • hypoalbuminemia: decreased bound Ca, thus tCa
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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
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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
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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)
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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
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11
Q

Increased bone mobilization or intestinal absorption of Ca leads to _______

A

Increased PTH or PTH-related protein

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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

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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
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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
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15
Q

Exogenous vs endogenous vitamin D

A
  • exogenous: rodenticide, some medicine, plants, dietary intake
  • endogenous: granulomatous inflammation, neoplasm-associated hypervitaminosis D
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16
Q

Neoplasia in bone

A

Lymphoma and myeloma

  • localized bone resorption and corresponding hypercalcemia
  • not associated with increased PTH, PTHrp, or vitamin D
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17
Q

Acute/chronic renal disease in horses

A

Due to decreased GFR

- lowering dietary Ca intake can reduce or eliminate hypercalcemia

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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)
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19
Q

30% of hypercalcemic dogs have ______

A

Hypoadrenocorticism

- might involve binding to protein or citrate and renal excretion

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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)
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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
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22
Q

Other mechanisms of hypercalcemia

A
  • IV infusion of Ca
  • hemoconcentraiton
  • juvenile onset hypothyroidism
  • retained fetus and endometriosis
  • idiopathic hypercalcemia in cats
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23
Q

Hypoalbuminemic hypocalcemia

A
  • decreased protein bound Ca

- [fCa] does not decrease, so no clinical signs of hypocalcemia (pseudo-hypocalcemia)

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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)

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25
Q

Pseudo-hypoparathyroidism

A

Unresponsive PTH receptors/pathways

- hypocalcemia

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26
Q

Hypomagnesemia

A

Functional hypoparathyroidism state and hypocalcemia

- adenylate cyclase impaired –> less PTH released and less response to PTH

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27
Q

Hypovitaminosis D

A

Chronic renal disease and failure in dogs, cats, cattle

  • abnormal vitamin D metabolism
  • protein losing nephropathy in dogs
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28
Q

Vitamin D receptor defect

A

Rickets

  • defective receptors and response to vitamin D
  • hypocalcemia
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29
Q

Exocrine pancreatic insufficiency in dogs

A

Incomplete digestion of dietary lipids and other ingesta

- frequently also have hypoalbuminemia that would contribute to hypocalcemia

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30
Q

Pregnancy, parturient, lactational

A

Ca lost to milk or fetal bone development

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31
Q

Hypercalcitonsim

A

Thyroid C neoplasms, reported in older bulls

- hypocalcemia

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32
Q

Nutritional hypocalcemia

A

Vitamin D deficient diets

- leads to secondary hyperparathyroidism –> increased bone mobilization (especially in young animals)

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33
Q

Oxalate toxicity

A

Ingestion of plants with high oxalate and low Ca contents

- horses and ruminants

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34
Q

Ethylene glycol toxicity

A

Excess renal excretion

- Ca binding to metabolites in renal tubular fluid

35
Q

Metabolic alkalosis

A

Plasma [HCO3] above the renal threshold –> excretion of Ca with the bicarb
- intravenous HCO3 infusion in cats

36
Q

Furosemide treatment

A

Inhibition of Na and Cl resorption –> less Ca resorption (depends on Na gradients)

37
Q

Hypocalcemia due to Ca binding with _____

A

Diffusible anions

- EDTA, oxalate, citrates

38
Q

Fracture healing

A

Early stages may contribute to hypocalcemia

39
Q

Acute pancreatitis may cause _____

A

Hypocalcemia

- common in dogs and cats

40
Q

Urinary tract obstruction

A

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
Q

Phosphate enema

A

Hyperphosphatemia

  • more Ca/PO4 compounds in plasma and complexes in tissues
  • increased excretion of PO4 and consequently Ca
42
Q

GI disorders in horses causes ______

A

Hypocalcemia

43
Q

Myopathies

A

Hypocalcemia may occur in several equine myopathies

44
Q

Acute tumor lysis syndrome

A

Released PO4 may form complexes and deposits with Ca and bind and inhibit Ca tubular resorption

45
Q

Rumen overload and hyperadrenocorticism in dogs also cause _____

A

Hypocalcemia

46
Q

[fCa] is tightly controlled by _____

A

Hormones

  • abnormal Ca regulation –> clinical signs
  • [tCa] often parallels [fCa] but not always
47
Q

Hypocalcemia caused by hypoproteinemia or hypoalbuminemia

A

[tCa] decreased (less protein-bound Ca)

- [fCa] may be WRI

48
Q

Hypercalcemia in renal failure or multiple myeloma

A

[tCa] increased (more bound Ca with abnormal globulin, citrate, or PO4}
- [fCa] may be WRI

49
Q

Hypocalcemia in urinary obstruction in cats

A

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
Q

Chronic renal failure in dogs

A

55% had decreased total or free Ca, 33% had increased

- changes in [tCa] did not correlate to changes in [fCa]

51
Q

Hyperthyriodism in cats

A

Decreased [fCa]

- [tCa] WRI

52
Q

Endurance sports in horses

A

Decreased [fCa]

- [tCa] WRI

53
Q

Blood transfusion

A

Massive transfusion of blood or plasma containing citrate as anticoagulant can cause decreased [fCa]

54
Q

Acidotic calves (due to diarrhea)

A

Both were decreased, but [tCa] was decreased more

  • both decreased after fluid therapy
  • therapy with NaHCO3 can rapidly decrease the [fCa]
55
Q

Change in blood pH affects binding to proteins and other anions

A
  • acidemia –> less binding –> increases [fCa]

- alkalemia –> more binding –> decreases [fCa]

56
Q

Organic acidosis

A

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
Q

Blood pH also affects [PTH]

A

Increased in experimental acidoses, decreased in alkaloses

58
Q

Routine assays measure

A

[tCa]

  • free
  • protein bound
  • bound to anions other than proteins
59
Q

Serum [fCa] values might be inaccurate when _______

A

Blood not handled properly

  • anaerobically
  • separate serum from clot immediately
  • no use of serum separator tubes
60
Q

Hypocalcemia values

A

Decreased protein/albumin = decreased bound

- normal [fCa] regulation: WRI

61
Q

Hypocalcemia with normal protein concentrations

A

Low [tCa] indicates decreased [fCa]

  • inadequate PTH or vitamin D activties
  • bound Ca is unchanged
62
Q

Severity of decreased [fCa] may not be evident from [tCa] if bound Ca is _____

A

Increased

  • chronic renal failure: abnormal vitamin D metabolism –> decreased [fCa]
  • increased citrate and PO4 –> increased [bound Ca]
63
Q

Hypocalcemia due to in vitro changes

A

Excess heparin in sample can cause falsely decreased [fCa]

- binding to heparin

64
Q

Hypercalcemic samples usually have high _____

A

[fCa]

  • PTH, PTHrp, vitamin D activities increased
  • bound Ca might be unchanged
65
Q

WRI [tCa]

A

Normocalcemia and hypoproteinemia

- suggests increased [fCa]

66
Q

[fCa] is affected by altered _______

A

Plasma pH and nonprotein anions

  • lactic acidosis –>
  • acidemia: decreases protein-bound
  • nonprotein anions: increased [bound Ca]
67
Q

Different forms of phosphorous

A
  • 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
Q

Renal clearance of PO4

A

Major route of excretion

- PTH is potent phosphaturic agent (inhibit resorption in distal tubules)

69
Q

Absorption of PO4 in intestines

A

Enhanced by 1,25 DHCC (calcitriol, metabolite of vitamin D)

70
Q

Resorption from bone

A

PTH stimulates osteocytes and osteoclasts to release PO4 from bone

71
Q

Shifting of PO4 between ICF and ECF

A

Insulin promotes entry into cells

72
Q

Animal age

A
  • growth hormone: increases renal resorption –> increased [Pi]
  • serum [Pi] is greater in young, growing animals than in the adult
73
Q

Decreased urinary PO4 excretion

A
  • 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
Q

Increased PO4 absorption from intestine

A
  • 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
Q

Shift from ICF to ECF

A

Myopathies (release from damaged muscle fibers)

- acute tumor lysis syndrome: release from necrotic neoplastic cells

76
Q

Pseudo-hyperphosphatemia

A

In cases of hyperbilirubinemia, monoclonal gammopathy, in vitro hyemolysis

77
Q

Other mechanisms of hyperphosphatemia

A
  • hyperthyroidism in cats
  • lactic acidosis
  • hyperadrenocorticisim in dogs
78
Q

Increased urinary excretion

A
  • prolonged diuresis: less PO4 is resorbed
  • increased PTH or PTHrp
  • fanconi syndrome: proximal tubular defect –> decreased resorption of glucose, amino acids, and PO4
79
Q

Decreased intestinal PO4 absorption

A
  • prolonged anorexia or PO4 deficient diet
  • PO4 binding agents
  • hypovitaminosis D
  • intestinal malabsorption
80
Q

Shift of PO4 from ECF to ICF

A
  • 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
Q

Defective mobilization of PO4 from bone

A
  • postparturient paresis (milk fever) and eclampsie

- inability to mobilize sufficient Ca and PO4 from bones to replace what is lost in milk

82
Q

Equine renal disease

A

May be seen in hypercalcemic cases, not a consistent finding

  • halothane anesthesia in horses
  • hypophosphatemia
83
Q

Pseudo hypophosphatemia due to conjugated

A

Hyperbilirubinemia

Clinical Pathology (9 decks)

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