Lecture 4 1/31/25 Flashcards
What is the mechanism of hypervitaminosis D?
increased intestinal absorption of Ca2+ and phosphrous
What are the causes of hypervitaminosis D?
*intoxication
–vit. D rodenticide
–topical anti-psoriasis cream
*excessive supplementation
–calcitriol
–dietary
What are the clinical features of hypervitaminosis D?
-can have a rapid increase in Ca
-acute PUPD
-acute renal failure
-tissue mineralization
-vomiting/anorexia/lethargy
-arrhythmias, seizures, death
What are the clin path features of hypervitaminosis D?
-tCa increases
-iCa increases
-phosphorus increases
-PTH of 0
-PTH-rp of 0
What is the mechanism of granulomatous disease?
-stimulated macrophages produce calcitriol
-leads to increased Ca2+ and P
What are the potential causes of granulomatous disease?
-infections
-sterile panniculitis
-granulomatous inflammation
Why are the clinical signs in granulomatous disease contributed to the disease and its cause rather than the hypercalcemia?
typically only see mild increases in Ca with granulomatous disease; not enough to see clinical signs
What are the characteristics of idiopathic hypercalcemia?
-most common cause of increased Ca in cats
-typically occurs in middle-aged cats, but can occur at any age
-mild to moderate increase in Ca
-must rule out other causes, especially lymphoma
What are the clinical signs of idiopathic hypercalcemia?
-may be asymptomatic
-hyporexia and weight loss
-vomiting
-constipation
-stones
What are the treatment options for cats with idiopathic hypercalcemia?
-diet change; increase fiber, decrease Ca (first rec)
-prednisolone
-PO bisphosponates
What are the characteristics of hypercalcemia associated with Addison’s disease?
-usually mild increased tCa
-possible normal iCa
-clinical signs NOT due to increased Ca
-mechanism unknown; theories include decreased renal Ca excretion, hemoconcentration, and increased protein binding of Ca
What are the non-pathologic mechanisms of hypercalcemia?
-young, growing animals; correlates to bone growth
-post-prandial
-spurious; due to hemolysis or lipemia
What are the effects of hypocalcemia on the neurons?
-Na+ channels are more likely to open
-neuron is easier to depolarize; threshold is lower
-neuron is more excitable; spontaneous muscle contractions more likely
What causes clinical manifestations of hypocalcemia?
excitability of neuronal and muscular tissues
What are the clinical manifestations of hypocalcemia?
-muscle tremors
-facial rubbing
-restlessness
-seizures
-hyporexia and weight loss
What is the approach to hypocalcemia?
-confirm hypocalcemia with an iCa measurement
-history
-clinical signs
-minimum database
-PTH measurement
-vit. D measurement
What are the steps of emergency treatment for hypocalcemia?
-10% calcium gluconate IV
-ECG monitoring
-benzodiazepines if seizures occur
What is the maintenance treatment for primary hypoparathyroidism?
calcitriol +/- calcium carbonate that is titrated to maintain iCa within the reference interval
Which diseases cause hypocalcemia?
-primary hypoparathyroidism
-eclampsia
-ethylene glycol toxicity
-acute pancreatitis
-renal failure
-severe gut disease
What are the mechanisms for hypocalcemia?
-decreased PTH
-decreased calcitriol/vit. D
-increased Ca utilization
-increased Ca consumption
What are the characteristics of hypoparathyroidism?
-decreased secretion of PTH
-can be primary or secondary/iatrogenic
What are the characteristics of primary hypoparathyroidism?
-destruction or atrophy of parathyroid glands
-usually immune-mediated
-clin path shows low PTH, tCa and iCa
-phosphorus is normal to increased on clin path
Which animals are most likely to develop primary hypoparathyroidism?
-young, female dogs
-poodles, mini schnauzers, german shepherds, and golden retrievers
What are the main clinical signs of hypoparathyroidism?
-seizures/tetany
-intense rubbing/pawing at face
-intense biting/licking at paws
-signs that worsen with excitement, exercise, and/or petting
What are the characteristics of primary hypoparathyroidism diagnosis, treatment, and prognosis?
-diagnosed through iCa and PTH measurements
-treated with lifelong calcitriol +/- calcium carbonate
-excellent prognosis
What are the characteristics of secondary hypoparathyroidism?
-occurs following thyroid, parathyroid, or other neck surgery
-PTH and iCa are low
-phosphorus is normal or high
What are the characteristics of calcitriol?
-active form of vit. D3
-fat soluble; obtained from diet
-activated in the kidney via alpha1-hydroxylase
What can cause decreased calcitriol/vit. D?
decreased gut absorption of vit. D/small intestinal malabsorption
What are the clinical signs of small intestinal malabsorption?
-weight loss
-vomiting and/or diarrhea
-ascites if albumin is low
What are the clin path signs of protein-losing enteropathy?
-panhypoproteinemia
-lymphopenia
-hypocholesterolemia
-decreased tCa and iCa
What must be done to determine if GI signs are due to hypocalcemia?
must measure iCa; clinical signs of hypocalcemia only occur if this measurement is low
What are the characteristics of hypocalcemia due to renal disease?
-tCa and iCa can be mixed and matched due to complexity of renal disease
-clinical signs are rarely due to hypocalcemia
-mechanisms include decreased renal activation of calcitriol, hyperphosphatemia, and complexed Ca
What are the characteristics of eclampsia?
-parathyroid glands are unable to respond to acute increases in calcium demand
-seen in lactating patients due to loss of Ca in milk and to the fetal skeletons
-can be life-threatening; often causes severe hypocalcemia
How is eclampsia diagnosed?
-history
-clinical signs
-measurement of tCa and iCa
How is eclampsia treated?
-IV calcium to start
-switch to PO calcitriol +/- calcium
-temporarily remove babies
When is eclampsia most likely to occur in dogs and cats?
dogs:
-within first 4 weeks of lactation
-more common in small breeds
cats:
-peak lactation
-also 3 to 17 days prior to queening
What are the characteristics of ethylene glycol toxicity?
-metabolites of ethylene glycol chelate calcium into calcium oxalate
-crystals form within renal tubules; leads to AKI and loss of calcium into urine
-clinical signs are rarely due to hypocalcemia
What are the characteristics of hypocalcemia associated with acute pancreatitis?
-typically mild hypocalcemia
-severe hypocalcemia indicates poor prognosis
-due to the saponification of peri-pancreatic fat
-clinical signs are rarely due to hypocalcemia
Which diseases do have clinical signs due to hypocalcemia, and which do not?
clinical signs DUE to low calcium:
-primary hypoparathyroidism
-eclampsia
-+/- gut malabsorption
clinical signs NOT DUE to low calcium:
-renal disease
-ethylene glycol tox.
-acute pancreatitis
