Parathyroid & Calcium Disorders Flashcards
Dr. Swan
What are calcium and phosphorus mediated by to maintain homeostasis?
- parathyroid hormone
- calcintonin
- vitamin D
- PTH-related protein
In homeostaiss, calcium and phosphorus are [directly/inversely] related
inversely
What stimulates PTH secretion?
low calcium
What effects does PTH have when released?
- stimulate calcium and phosphorus osteolysis from bone
- increase Ca2+ absorption in intestine
- kidney: increase Ca2+, waste phosphorus
What is calcitonin stimulate by?
high calcium
What effects does the release of calcitonin have on the body?
- increase calcium and phosphorus absorption in bone
- decrease Ca2+ absorption intestine
- excrete Ca2+, absorb phosphorus
What is the stimulus to produce vitamin D in the kidney?
- low calcium
- high PTH
What effects does vitamin have on the body?
- osteolysis to increase Ca2+ and PO4-
- increase intestinal absorption of both Ca2_ and PO4-
What can inhibit vitamin D?
high levels of Ca2+ and PO4-
How does insulin impact PO4-?
drives absorption of PO4- into cells (lowers it in blood as a result)
When cells burst, you can see [increased/decreased] levels of phosphorus
increase
What is a major source of Ca2+ and PO4-?
mammary gland
lactation stimulus —> from blood to gland
Total calcium is composed of 3 fractions which are _____
- ionized/free calcium ~50%
- protein-bound calcium 40-45%
- calcium complexed with salts ~5-10%
Which calcium is the bioactive and available form of calcium?
free/ionized calcium - results in clinical signs of hypercalcemia
Look at the chart for hypercalcemia
What does primary hyperparathyroidism result in?
chief cell adenoma or carcinoma - often functional tumors which produce PTH!
What is Humoral Hypercalcemia of Malignancy (HHM)?
also called pseudo-hyperparathyroidism
neoplastic cells produce PTHrP which has similar homology and function as PTH
What is Humoral Hypercalcemia of Malignancy associated with?
neoplasia - associated with PTHrP production
Neoplasia of HHM is associated with PTHrP production which causes
- anal sac gland adenocarcinoma (AGASACA)
- lymphoma
- various carcinomas
run malignancy profile
Besides neoplasia, _____ can also act through the PTHrP mechanism
schistosomiasis (increases calcium)
What is the effect of vitamin D toxicosis on calcium and phosphorus?
both elevated
What is the pathophysiology of hypervitaminosis D?
supplementation with vitamin D / vitamin D rodenticides, plants —> increased calcium and phosphorus absorption from gut and bone —> metastatic mineralization of tissues
What is the effect of granulomatous disease on calcium and phosphorus?
both elevated
How does granulomatous disease act? Which diseases?
act through vitamin D-mediated mechanism as above
fungal disease
What has been reported with raisin and grape toxicosis?
acute hypercalcemic renal failure
With renal insufficiency or failure, what are the calcium levels?
horses: high calcium, low phophorus
dogs/cats: low calcium, high phosphorus
How does multiple myeloma cause hypercalcemia?
causes increased binding of calcium to globulins which increases total calcium (and protein-bound)
iCa2+ expected to be WRI
What else causes hypercalcemia?
hypoadrenocorticism
What is the Law of Mass Action (metastatic mineralization)?
if Ca2+ x PO4- > 70, then your patient is at risk for metastatic mineralization of the tissues
Regarding hypercalcemia and the law of mass action, when do you know there is ACTIVE mineralization?
if Ca2+ x PO4- > 100
What are the first tissues to mineralize via hypercalcemia?
- kidneys - exacerbates renal disease and mineralize first
- lungs
- GI tract
What are causes of hypocalcemia?
- hypoalbuminemia
- hypoparathyroidism
- hypovitaminosis D
- look over
Explain hypocalcemia and hypoalbuminemia. Phosphorus levels?
most common cause of mild hypocalcemia - can’t bind to calcium
phosphorus iei WRI
Explain hypocalcemia and hypoparathyroidism. Phosphorus levels?
- primary from a damage of parathyroid gland
- pseudo due to decreased PTH receptor sensitivity to calcium, grass tetany
high phosphorus
Explain hypocalcemia and hypovitaminosis D. Phosphorus levels?
- chronic renal disease
- protein-losing enteropathies (PLE)
- vitamin D deficiency
Why does grass tetany cause?
hypomagnesemia and hypocalcemia
- occurs in ruminants grazing in lush spring pastures
What does hypomagnesemia cause?
a functional hypoparathyroid state (decreased PTH sensitivity)
Who is more at risk for milk fever / puerperal tetany (eclampsia)?
cattle: post-parturient
small ruminants: peak lactation with multiple kids
small breed dogs with large litters
Look at the other toxicities associated with hypocalcemia
What are clinical signs of hypocalcemia?
- face rubbing
- muscle fasciculations
- anxiety, restlessness, or confusion
- hypersensitivity to touch
- aggression
- hyperthermia
- seizures and/or tetany
Look at chart for hyperphosphatemia
What are causes of hyperphosphatemia
- myopathies
- tumor lysis syndrome
- acromegaly
Look at chart for hypophosphatemia
What is fanconi syndrome, and what is it associated with?
hereditary defect reported in dogs
causes decreased tubular resorption of glucose, amino acids, and PO4-
- often see mild glucosuria, as well as proteinuria, and adequately concentrated urine
Prolonged anorexia results in _______
hypophosphatemia
What is magnesium most stored in?
bone
Look at chart for hypermagnesemia
Look at chart for hypomagnesemia
What do you do if you suspect malignancy and hypercalcemia?
elevations in iCa2+ —> malignancy panel (iCa2+, PTH, PTHrP)
What do you do if you suspect malignancy and hypocalcemia?
decreases in iCa2+ —> treat and consider if further diagnostics are needed if persistent
A patient’s malignancy panel is shown. What is your conclusion?
hypercalcemia due to Humoral Hypercalcemia of malignancy (look for neoplasm!)
A patient’s malignancy panel is shown. What is your conclusion?
hypercalcemia due to parathyroid-related state (most likely primary hyperparathyroidism)
