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Clin path test 4 > Calcium, Phophorus, & Magnesium > Flashcards

Calcium, Phophorus, & Magnesium Flashcards

1
Q

Parathyroid gland

A
  • Main endocrine organ controlling Ca/P metabolism
  • Live on the thyroid gland
  • Chief cells
    • if low Ca PTH made
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2
Q

PTH

A
  • Mobilizes Ca and P from bone
  • Makes kidneys save Ca
  • Makes kidneys make most active form of vitamin D
    • Vitamin D makes GI absorb Ca and P
  • net effect PTH => kidneys pee out Phosphorus (inc Ca dec P)
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3
Q

Vitamin D

A
  • made in kidney
    • stimulated by PTH
  • Actions
    • Inc GI absorption of Ca and P***
    • Inc bone resorption
    • Inc renal resorption
  • inc Ca and P in the blood
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4
Q

Calcitonin

A
  • PTH antagonist
  • Produced by C cells of thyroid gland
  • Stimulated by high Ca+
  • Inhibits reabsorption of Ca and P from bone and kidney
  • dec Ca and dec P
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5
Q

Serum Calcium

Total Ca

Free (ionized Ca)

A
  • 40% bound to albumin
  • 50% ionized (active and regulated)
  • 10% complexed
  • Total Calcium
    • provided with serum biochem profile
  • Free (ionized) Calcium
    • can be measured with certain machines
    • portion that is hormonally regulated and contributes to pathologic states
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6
Q

Ca Concentration depends on

A
  • 1) dietary intake
  • 2) intestinal absorption (duodenum)
    • inc by calcitrol (active vit D3)
    • dec by malabsorption, maldigestion, cortisol
  • 3) skeletal resportion
    • modified by: PTH, Calcitonin, Age, Osteolytic dz
  • 4) renal reabsorption and excretion
    • modified by: PTH in distal tubules
    • Ca removed based on GRF in proximal tubules and loop of Henle
  • 5) other losses
    • saliva, lactation, fecal, sweat (horses)
  • 6) Regulatory hormone concentrations
    • PTH, Calcitriol, Calcitonin, PTHrP, others
  • 7) Acid base status
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7
Q

pH effects

Acidosis:

Alkalosis

A
  • Acidosis => inc ionized Calcium (free Ca)
  • Alkalosis => dec ionized Ca

* in acidosis, Hydrogen ions take up space on albumin and more Ca is in blood

*in alkalosis, fewer Hydrogen ions are on albumin and more Ca is bound, and less free Ca in blood

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8
Q

Analytes for Ca status

A
  • Total calcium: standard analyzer
  • Free (ionized) Ca: ion specific electrode
  • Inorganic phosphorus: standard analyzer
  • Parathyroid hormone (PTH): immunoassay
  • Parathyroid hormone related peptide (PTHrp): immunoassay
  • Vitamin D
  • send Ca panel to Michigan state
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9
Q

Hypocalcemia: Hypoalbuminemia

A
  • 40% Ca bound to albumin
    • dec albumin = dec total Ca
  • free (ionized) Ca stays the same
  • benign
  • Most common cause of dec in total Ca
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10
Q

Free (Ionized Ca conc)

A
  • Inferred from
    • total Ca conc
    • Albumin conc
    • Acid base status
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11
Q

Hypocalcemia

A
  • Inapparent with mild dec Ca
  • inc neuron excitability (low Ca = easier signal conduction)
    • nervous, trembling, panting, m. fasciculation, stiff gain, muscle cramping
  • Cats
    • intense facial rubbing, licking paws, tetanic paralysis
  • Cows
    • flaccid paralysis, seizures
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12
Q

Hypocalcemia Causes

A

HARP IS ALE

  • Hypoparathyroidism, Hyperparathyroidism (secondary, nutritional)
  • Albumin (hypoalbuminemia)
  • Renal failure (not horses)
  • Pancreatitis, Phosphorus (hyperphosphatemia)
  • Intestinal malabsorption, intracellular shift
  • Spurious, sepsis
  • Alkalosis
  • Lactation
  • Ethylene Glycol
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13
Q

Hypoparathyroidism

Hyperparathyroidism

A
  • Hypoparathyroidism
    • less PTH production
      • => less Ca released from bone
      • => More Ca lost in urine
    • Less active Vitamin D made
      • => less Ca uptake from GI
  • Nutritional/secondary Hyperparathyroidism
    • Improper diet formulations => hypocalcemia (low Ca or Vit D)
    • Hyperparathyroidsim => secondary in an attempt to correct blood Ca level
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14
Q

Renal Failure and hypocalcemia

A
  • Dec calcitriol (active Vit D3) formation by kidney
    • dec intestinal absorption of Ca
    • PTH less effective at releasing Ca from bone
  • Inc P will dec Ca
  • Ionized Ca is low more often than total Ca
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15
Q

Pancreatitis

Phosphorous (hyperphosphatemia)

A
  • Pancreatitis => we don’t really know
  • hyperphosphatemia
    • phosphate containing enemas
    • mineralization of soft tissue when Total Ca X P > 70
  • Avoid Ca supplementation unless
    • seizure, twitching, tremor, sev hypocalcemia
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16
Q

Intestinal malabsorption

Intracellular shift

A
  • Intestinal malabsorption
    • Dec absorption of Ca ++ and Vit D
    • Concurrent panhypoproteinemia
  • Intracellular shift
    • pancreatitis
    • myopathies: Ca can move intracellulary in necrosis
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17
Q

Spurious

Sepsis

A
  • Spurious
    • contamination of samples with EDTA (chelates Ca to keep blood from clotting)
    • K in tube => pseudohyperkalemia
  • Sepsis
    • Mechanism….?
    • check free (ionized) Ca in critically ill
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18
Q

Lactational Hypocalcemia

A
  • Eclampsia
    • emergency medical condition
    • life-threatening drop in blood Ca in nursing mothers
    • occurs when puppies are 1-5 weeks of age
    • CS
      • Puerperal tetany
        • stiff limbs, inability to stand or walk
      • tremors, weakness, paralysis
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19
Q

Eclampsia

(periparturient hypocalcemia)

A
  • 1-3 weeks post partum
  • Small breed dogs
  • Loss of Ca in milk/skeletal development
  • Seizures, trembling, twitching, shaking, stiffness
  • Treatment: IV Calcium gluconate
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20
Q

Periparturient hypocalcemia

  • 4 year old Hostein cow, flaccid paralysis
A
  • Dystocia, uterine torsion diagnosed at dairy
  • Ionized-Ca2+ 0.6 1.1-1.3 mm/L (range)
  • Excess Ca loss due to fetal skeletal development and loss in milk
  • Inadequate absorption from intestine/release from bone
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21
Q

Ethylene Glycol

A
  • metabolites of this toxin bind Ca++
  • Can result in hypocalcemia and Ca++ Oxalate Crystalluria
  • Intoxication with oxalate containing plants can also cause hypocalcemia
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22
Q

Significance of hypercalcemia

A
  • Approximately 5% are young growing animals
  • Approximately 60% are transient (not worked up)
  • Approximately 15% persistent and pathological
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23
Q

Hypercalcemia

CS

A
  • PU/PD-Inhibits ADH, dysregulation of aquaporins
  • Lethargy, weakness, constipation
  • Mineralization of soft tissue - when Calcium X Phosphorus > 70
  • Calcium containing uroliths
24
Q

Hypercalcemia Causes

GOSHDARNIT

A
  • G: Granulomatous
  • O: Osteolysis
  • S: Spurious
  • H: Primary Hyperparathyroidism
  • D: Vitamin D Toxicosis
  • A: Addison’s Disease, Age
  • R: Renal Disease
  • N: Neoplasia
  • I: Idiopathic
  • T: Hypothermia
25
Q

Hypervitaminosis D

Cause

A
  • Vitamin D toxicity
    • Over supplementation with dietary source
    • Exposure to owner medications
    • Rodenticides with Cholecalciferol (vit D precurs.)
    • Plants containing vitamin D glycosides
      • Cestrum diurnum, Solanum malacoxylon
    • Granulomatous disease
      • Activation of Vitamin D by macrophages
26
Q

Hypervitaminosis D

Mechanisms

A
  • Vitamin D inc Ca resorption of bone
  • Vitamin D inc Ca & Phosphorus absorption from intestine
  • Hypercalcemia & hyperphosphatemia
  • These patients at greater risk for soft tissue mineralization
27
Q

Spurious hypercalcemia

A
  • Lipemia, sample handling
  • hemolysis
  • mostly young dogs
28
Q

Hypercalcemia

Primary Hyperparathyroidism

A
  • Hormones secreted by
    • functional adenoma (more common)
    • Hyperplastic gland
    • Functional carcinoma
  • Do more advanced panel
    • PTH
29
Q

Hypoadrenocorticism/Addison’s

A
  • Common cause of hypercalcemia in dogs
  • Total Ca inc +/- ionized Ca
  • May be inc reabsorption of Ca
  • Responds to corticosteroid tx and/or volume replacement
30
Q

Hypercalcemia

Renal Failure

A
  • horse thing renal failure
    • commonly associated with inc Ca
      • dietary
      • inc intestinal absorption
      • do not activate Vit D in kidney
    • Ionized Ca normal to low

*important for distinguishing from hyperparathyroidism with secondary renal failure

31
Q

Chronic renal failure

A
  • Hypercalcemia is common in horses
  • iCa usually normal to low
  • PTH often elevated
  • In dogs, inc total Ca due to inc complexed Ca (ionized and protein-bound normal) (24% vs 11% complexed protein) phosphates, citrates, lactates, bicarbonates, oxalates

*Important when distinguishing from hyperparathyroidism with secondary renal failure

32
Q

Humoral hypercalcemia of malignancy

A
  • Humoral hypercalcemia of malignancy
    • Most common cause of hypercalcemia
  • Lymphoma
  • Apocrine gland adenocarcinoma of anal sac
  • Multiple myeloma
  • PTH-related protein
    • similar in structure and funtion to PTH
    • can be produced by tumors
    • measure in dogs and cats
  • other compounds secreted by tumors such as Vit D like steroid and osteoclast activating factor
33
Q

4 year old MC Golden Retriever

Humoral hypercalcemia of malignancy

A
  • Apocrine gland adenocarcinoma: anal gland
  • Ionized Calcium: 1.8 mmol/L (normal 1.25-1.45)
  • Intact PTH: 0.00 pmol/L (normal 3.00-17.00)
  • PTHrp: 5.9 pmol/L (normal 0.0-1.0)
34
Q

Idiopathic hypercalcemia

A

cat thing

rule out other causes

not for other species

35
Q

Further diagnostics for hypercalcemia

A
  • Ionized calcium
  • CBC, Serum chem profile, UA
  • Thorough physical exam
    • palpate anal area, lymph nodes
    • radiography/ultrasound (Parathyroid glands)
  • Measure PTHrP
  • Measure PTH
  • Measure Vit D
36
Q

Phosphorus

A
  • Mineralization of bone
    • 85% of P in bones and teeth
  • Critical for high-energy phophoryl units of metabolic intermediates
    • Remaining 15% is in high energy bonds (ATP), DNA, Phospholipids, intracellular acid base buffering
  • Structural phosphoproteins and phospholipids
  • Inorganic phosphate anions play a role in acid base metabolism
37
Q

Phosphorus regulation

PTH

Calcitonin

Vit D

Growth Hormone

A
  • PTH: decreases P
    • decreases tubular reabsorption
  • Calcitonin: decreases P
    • inhibits bone resoprtion
    • inc movement into tissues
    • dec renal tubular resporption
  • Vitamin D: increases P
    • ​stimulates absorption from intestine and kidney
    • inhibits PTH synthesis
  • Growth Hormone: Increases P
    • ​increases renal tubular resorption
38
Q

Chem stats common in young, growing animals from bone growth

A
  • inc P
  • inc Ca
  • inc ALP
39
Q

Abnormal P conc

A
  • Clinical signs usually due to underlying dz
  • Assoc with disorders of Ca homeostasis
    • i.e. intestinal malabsorption
  • Phosphorus concentrated intracellularly
  • Shifts between ICF and ECF
    • ​Insulin promotes P entry into cells
    • Bicarb shift P into cells
40
Q

Insulin and Phosphorus

A
  • Promotes P entry into the cells
    • for phosphorylation of glucose
    • decreases serum P
41
Q

Bicarb and Phosphorous

A
  • Bicarb shifts P into cells
    • alkalemia stimulates PFK enzyme activity in glycolysis
    • promotes P movement into RBCs
      • b/c of increased phosphorylation during accelerated glycolysis
    • decreases serum P
42
Q

Hyperphosphatemia

A
  • Can induce bone resorption
    • high phosphorus chelates Ca
    • lowers ionized Ca
    • Activates PTH secretion
    • Inc bone resorption
    • Demineralizes bone
    • Fibrous osteodystrophy results
  • Can cause soft tissue mineraliztion
    • if also hypercalcemic
    • when Ca X P > 70
43
Q

Hypercalcemia may result in mineralization of kidneys =>

A
  • could lead to dec GFR
    • subsequent normal or inc serum P conc instead of decreased
44
Q

Hyperphosphatemia - causes

A
  • Decreased renal excretion - #1 cause (Dec GFR)
    • Azotemia
      • pre
      • renal
      • post
    • Herbivores may compensate via intestine
      • cows and horses in renal failure can have normal to low P
    • ruptured bladder/urethral obstruction
  • Disorders of Ca homeostasis
    • Vit D intox
    • Primary hypoparathyroidism
  • Growing animals (bone remodeling)
  • Shift from intracellular to extracellular fluid
    • Tissue trauma, rhabdomyolysis
    • Acute tumor lysis syndrome: chemo in animals with high tumor burden
  • Iatrogenic
    • diet, fluids, enemas
45
Q

Hypophosphatemia-causes

A
  • Anorexia, decreased intestinal absorption
  • Disorders of Ca homeostasis
    • primary hyperparathyroidism
    • hypercalcemia of malignancy
    • Vitamin D deficiency
  • Shift from extracellular to intracellular fluid
    • with insulin (refeeding syndrom, diabetes treatment)
    • Alkalosis
  • Equine renal failure
    • hypercalcemia
    • hypophophatemia
  • Parturient paresis (milk fever)
    • Lactation
  • Iatrogenic
    • phosphate binding antacid
46
Q

Hyposphasphatemia

CS

A
  • < 1.5mg/dL => abnormally low ATP levels => intravascular hemolysis
  • Neuromuscular signs
    • Intestinal ileus
    • Weakness
    • Ataxia
    • Seizures
47
Q

11 year old MI Dalmation

  • Disorientation, ataxia, vomiting for 36 hours
  • indoor, no known tox exp, currently up to date and healthy
  • Weakness, fine tremors
  • Other PE findings WNL
A

Rule outs!

G: granulomatous

O: osteolysis

S: spurious

H: 1 hyperparathyroidism

D: Vitamin D toxicosis

A: Addison’s

R: renal

N: neoplasia

I: Idiopathic

T: Hypothermia

Primary hyperparathyroidism: removed tumor

48
Q

Alk Phos (ALP)

A
  • Smaller increases more impressive in cats
    • shorter half-life
  • Dogs: can be induced by
    • glucocorticoids
    • phenobarb
49
Q

Post op hemi parathyroidectomy

A
  • Hypocalcemia
    • unaffected parathyroid tissue atrophied
    • PTH short half life: dec Ca2+ 6-8 hours postop
    • Vitamin D supplemention likely necessary
      • may need to start tx before sz
      • goal: maintain low-low normal Ca
      • stimulation regrowth of atrophied parathyroid tissue
      • slowly withdraw Vit D over period of months
  • Hypomagnesemia
    • chronic hypercalcemia can cause hypoMg
    • signs sim to dec Ca, distinguished by hypertension
  • Infection/wound healing
50
Q

Magensium

A
  • Free part and protein bound part
  • Dietary intake and renal excretion
  • Imp role in PTH synthesis and release
  • Facilitates Na/K-ATPase activity in cell membranes
    • enzyme co-factor for all that use ATP
  • Structural role in bone formation
  • Imp in neuromuscular function
51
Q

Hypomagensemia

Causes

A
  • Hypoproteinemia
  • Dec intake (anorexia)
  • Dec absorption
    • enteric dz
    • grass tetany in cattle
  • inc excretion
    • diuresis
52
Q

Hypomagnasemia

NAVLE

A
  • Decreased intake
    • most common cause in ruminants
    • Lush green pasture high in K+ and low in Mg++
      • Grass tetany
      • K+ blocks normal Mg++ absorption in rumen
    • Older calves fed milk-only diets
      • ​Milk tetany
    • Prolonged anorexia
    • Poor diet
      • esp if lactating
    • Prolonged IV fluid therapy or parenteral nutrition w/out Mg supplementation
53
Q

Cantharidin Toxicity

A
  • Cantharidine from blister beetle
  • GI and Urinary mucosal irritant
  • Hypomagnesemia/Hypocalcemia
    • MOA unknown
54
Q

Manifestations of Hypomagnesemia

A
  • Secondary hypokalemia due to renal wasting of K
    • hypoMg may lead to reduced Na, K-ATPase function
    • dec function of Na-K-Cl cotransporter
    • Mg maintains intracellular K levels
      • if Mg low, K leaks from cells to ECF and lost from body b/c of decreased reabsorption in kidneys
  • Impaired PTH production and release leading to secondary hypocalcemia
55
Q

Hypomagnesemia

CS

A
  • Those associated with secondary electrolyte abnormalities
    • ​hypokalemia
    • hypocalcemia
  • ​Neuromuscular and cardiac abnormalities
    • Hyperexcitability
    • Tremors, fasciculations, ataxia
    • Frank tetany
    • Cardiac arrhythmias/possible arrest
56
Q

Female Herefor due to calve in 3 weeks

  • aggressive
  • fine tremors
  • 6 other similar cases recently died
  • fed mix of alfalfa and grass
A

Calcium = 9.1 (7-9.8)

Phosphorous = 5.2 (4.4-7.5)

Magnesium = 1.1 (1.9-3.5)

57
Q

Hypermagnesemia

A
  • Dec GFR/dehydration
  • Clinically less significant
  • Worry if acute
    • iatrogenic
    • dec GFR
      • ​dehydration
      • acute renal failure
      • urethral obstruction
    • patients can dev
      • CV probs
      • Neuro probs
        • flassid paralysis => resp arrest
      • nausea/vomiting

Clin path test 4 (9 decks)

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