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Disorders of Calcium Metabolism (Hypocalcemia (signs (may have no signs,…
Disorders of Calcium Metabolism
Calcium
total circulating calcium is sum of:
protein bound Ca (albumin, globulin)
complexed Ca (bicarb, phosphate)
ionized Ca (metabolically active)
parathyroid hormone
major regulator of Ca
increase ionized Ca conc
min to min control
calcitrol
(bioactive Vit D)
major regulator of Ca
increased ionized Ca conc
day to day control
dogs and cats require Vit D from their diet
calcitonin
decreases ionized Ca
Hypercalcemia
high blood Ca levels
signs
PU/PD, anorexia most common
"groans"
vomiting, depression, weakness, constipation
"bones" (related to underlying condition)
lameness due to bone destruction
"stones" (chronic hypercalcemia)
urolithiasis
differentials
GOSH DARN IT
granulomatous disease
osteolytic disease
spurious
hyperparathyroidism
drug related
Addison's disease
renal failure
nutritional neoplasia
idiopathic
tumor/toxin (excess Vit D)
diagnostics
measure ionized Ca
total Ca has a lot of false pos
measure phosphate levels
serum Ca-P
total Ca x P >70% = urgent treatment required
can help narrow down differentials
imaging: look for tumors
baseline cortisol/ACTH stim - rule out Addison's
calcidiol - rule out Vit D toxicity
treatment
individual based on patient
remove underlying causes (chemo, surgery)
IV fluid therapy (0.9% NaCl)
glucocorticoids if needed (only after definitive diagnosis)
Hypocalcemia
low blood Ca levels
due to increased excitability of neuromuscular junction
signs
may have no signs
muscle tremors/fasciculations
seizures
facial rubbing
muscle cramping
stiff gait
behavioral changes (hypersensitivity, aggression, restlessness)
anorexia, pyrexia, tachycardia (prolonged QT interval), prolapsed 3rd eyelid (in cats)
PU/PD, hypotension, respiratory arrest (uncommon)
differentials
postpartum hypocalcemia (common)
usually 1-3 weeks postpartum
common in small breed dogs with large litters
signs: seizures, trembling, twitching, stiffness
acute pancreatitis (common)
chronic renal failure (common)
milk fever (paturient paresis)
dairy cows and goats
occurs at onset of lactation from increased Ca levels
hypoparathyroidism (occasional)
more common in dogs
destruction of parathyroid gland
suppression of parathyroid hormone secretion
ethylene glycol toxicity (anti-freeze, occasional)
acute renal failure (uncommon)
rickets (uncommon)
diagnostics
rule out lab sampling error
measure total and ionized Ca and parathyroid hormone
treatment
manage underlying disease
IV Ca gluconate, oral Ca supplements, or calcitrol if tetany or seizures are occurring
calcitrol, oral Ca carbonate for hypoparathyroidism