Lecture 5 Flashcards by Lauren Nykanen

What type of calcium is active in the body?

Ionized free form

Makes up about 50% of total calcium

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Which calcium is provided on your serum biochemical profile?

Total calcium i.e. protein bound (40%), ionized (50%), and complexed (10%)

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What are five functions of calcium?

Cell signaling, muscle contraction/nerve conduction, gene transcription, calcium mediated excitation, voltage dependent ion channgels

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What does calcium concentrations depend on?

Dietary intake
Absorption by small intestine
Skeletal release

Renal reabsorption and excretion

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What increases small intestinal absorption?

Decreases?

Increased by calcitriol (vit D), lactation, growing animals, acid in diet

Decreased by malabsorption, cortisol/steroids, thyroxin, chronic acidosis

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What modifies the skeletal release of calcium?

PTH, calcitonin, age, osteolytic disease

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What dictates renal excretion of calcium?

PTH, calcitriol, and calitonin action on distal tubules

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What is the main endocrine organ involved in Ca/P metabolism?

Where does it come from?

What does it do?

PTH from chief cells of parathyroid gland

Increases Ca and decreases P

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Where is calcitriol made?

What is it stimulated by?

What does it do?

Made in kidneys

Stimulated by PTH

Increases GI absorption of Ca and P, increases bone release, increases renal reabsorption
Basically increases both Ca and P

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Where does calcitonin come from?

What does it do?

Produced by C cells of thyroid gland

Decreases serum Ca and P by inhibiting PTH

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What protein is 40% of ca bound to?

Albumin

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What is the most common cause of hypocalcemia of total calcium in all species?

Hypalbuminemia

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Hypcalcemia caused by hypoalbuminemia affects which pool of Ca?

Is this serious?

Total calcium

Ionized calcium stays the same

*this is benign

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What can cause hypoalbuminemia?

Increased loss or decreased production

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When you can’t measure it directly, what can you use to infer ionized calcium concentration?

Total calcium concentration
Albumin concentration
Acid base status

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If you need ionized calcium, should you use correction formula?

No! Measure directly because the correction formula is very faulty

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How does acidosis affect ionized calcium?

Alkalosis?

Acidosis increases ionized calcium while alkalosis decreases ionized calcium

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What are causes of hypocalcemia?

Hypoparathyroidism
Hypoalbuminemia
Renal disease (not horses)
Pancreatitis
Intestinal malabsorption
Spurious/artifact
Alkalosis
Lactation
Ethylene glycol

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When do clinical signs of hypocalcemia occur?

Why do these signs occur?

Only when ionized ca is low

Signs occur due to increased neuron excitability

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What are clinical signs of hypocalcemia?

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Nervousness
Trembling
Excessive panting
Muscle fasciculation and/or cramping
Stiff pelvic gait
Cats:facial rubbing and paw licking and tetanic paralysis
Cows: flaccid paralysis

Which causes of hypocalcemia are most common besides hypoalbuminemia

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Renal disease (not horses)
Pancreatitis
Eclampsia/milk fever

How does kidney disease cause hypocalcemia?

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Decreased calcitriol formation by the kidney

Ionized calcium is low more often than total calcium

Describe hypocalcemia from eclampsia (common presentation, treatment, etc)

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1-3 weeks post partum in small breed dogs
Seizures, trembling, twitching, shaking, stiffness
Treat via IV calcium gluconate but watch the heart

Describe hypocalcemia due to milk fiver

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Dairy cows- flaccid paralysis

Classic S-shape curve in neck

What are clinical signs of hypercalcemia?

PU/PD Lethargy, weakness, constipation Mineralization of soft tissue Calcium containing uroliths

Causes of hypercalcemia

``` Granulomatous disease Osteolysis Spurious/iatrogenic Primary hyperparathyroidism Vitamin D toxicosis Addison’s disease Renal disease Neoplasia Idiopathic (cats) Hypothermia ```

Primary hyperparathyroidism causing hypercalcemia

Increases total calcium, ionized calcium, PTH, and calcitriol (or may be normal) Decreases phosphorus (or may be normal)

Hypervitaminosis D causing hypercalcemia Causes?

Can be from oversupplementation, rodenticides, Vitamin D containing medications, plants containing Vit D precursors, granulomatous disease (activation of macrophages releases vitamin D

What does hypervitaminosis D do?

Increases Ca release from bone, Ca absorption in the intestine, phosphorus absorption *so patients will have high calcium and high phosphorus

What is the second most common cause of hypercalcemia in dogs?

Addison’s disease

What does Addison’s do to calcium?

Increases total and ionized calcium Physiology not known

What does renal disease do in horses?

Causes hypercalcemia

What does renal disease do in small animals?

Usually causes hypocalcemia HOWEVER, hypercalcemia in small animals can lead to renal disease

What is the most common cause of hypercalcemia?

Hypercalcemia of malignancy

What tumors can cause hypercalcemia

Lymphoma, apocrine gland adenocarcinoma of anal sac, multiple myeloma *usually associated with PTHrP production

Where is most of your phosphorus?

In your bones and teeth The other small percentage is in high energy bonds

How does PTH, calciltonin, vit D, and growth hormone affect phosphorus?

PTH and calcitonin decrease P Vit D and growth hormone increase P

What does hyperphosphatemia cause?

Induces bone resorption | Can cause soft tissue mineralization if also have high Ca

What is the number 1 cause of hyperphosphatemia?

Decreased renal excretion from decreased GFR from prerenal azotemia or renal disease

What are other causes of hyperphosphatemia?

``` Disorders of Ca homeostasis Growing animals (bone remodeling) Shifts from intracellular to extracellular fluid Iatrogenic Spurious ```

Causes of hypophosphatemia

``` Disorders of Ca homeostasis Shifts from ECF to ICF Equine renal disease Milk fever Iatrogenic ```

Differentials for hypophosphatemia

``` Primary hyperparathyroidism Hypercalcemia of malignancy Vit D deficiency Respiratory alkalosis Decreased intestinal absorption of P Renal tubular defects Chronic renal disease in horses ```

What signs may occur with hypophosphatemia?

Iv hemolysis | Neuromuscular signs

What does magnesium do?

Has a role in PTH synthesis and release Facilitates Na/K ATPase activity Bone formation Neuromuscular function

How is mg controlled?

Mainly through renal excretion

What clinical signs will you see with hypomagnesemia

Those associated with electrolyte abnormalities | Neuromuscular and cardiac abnormalities

What are some causes of low mg

Increased loss- most common cause in small animals (renal or GI) Decreased intake- most common cause in ruminants

Manifestations of hypomagnesemia

Secondary hypokalemia due to renal wasting of K | Impaired PTH production leading to secondary hypocalcemia

Lecture 5 Flashcards

(48 cards)