Parathyroid Disease Flashcards
where are all the calcium stores in the body?
ionized calcium, protein bound calcium, and complexed calcium
we usually measure total calcium which is ionized and protein bound
since most ingested calcium is excreted in the feces, what does it rely on to be absorbed?
calcitriol (activated vitamin D)
what are the cells that make PTH?
cheif cells
when calcium is too high…
PTH increases
what does PTH do
increases calcium reabsorption in the kidney and increases phosphorus excretion
increases calcium and phosphorus mobilization from bones and
increases calcium & phosphorus absorption via GI
Net effect is increase in calcium and decrease in phosphorus
youre presented with a young aged dog that has hypercalcemia and isosthenuria, and per the owner the dog seems to be drinking more and “slowing down”. What are your differentials?
lymphoma, addisons, PHPTH, CKD, lab error, anal sac adenocarcinoma, vitamin D toxicosis, young age
explain the pathophys behind primary HPTH
usually a solitary functional parathyroid adenoma that secretes PTH, and normal negative feedback lost
what is the number one clinical sign of PHPTH and why?
PUPD because excess calcium blocks ADH receptors and decreases sodium resorption
most dogs will NOT have clinical signs early on
others; weakness, decreased appetite, exercise intolerance
with PHPTH what changes will you expect on chemistry panel and UA?
chemistry: hypercalcemia (usually mild and static), hypophosphatemia
UA: isosthenuria then hyposthenuria, calcium oxalate crystals possible, can have a UTI
a dog named Peepeepoopoo comes to you because he is “ADR”, and the owner thinks he asks to go outside more often. You do a chemistry panel and find hypercalcemia. You dont do a full UA, but peepeepoopoo pees on the floor of your exam room and you get a USG quick that reads 1.019. You suspect PHPTH. What further diagnostic tests do you want to do?
PTH assay: in a normal dog with high calcium PTH would be low, so with PHPTH it would be high calcium and high PTH
PTHrp assay: this is cancer mimicking PHPTH so this should be negative
ionized calcium: will be elevated
vitamin D: to rule out intoxication
could also do a neck ultrasound
peepeepoopoo’s PTH results come back and they are very high. given that he is also hypercalcemic, you diagnose PHPTH. What treatment will you offer?
The hypercalcemia isn’t high enough to worry about
surgery: if done, doesn’t recur and excellent prognosis
on routine bloodwork for Smitten the cute kitten, you find she’s hypercalcemic. What things usually cause hypercalcemia in a cat?
neoplasia (lymphoma, SCC, retrovirus)
renal disease (50% with stones)
the rest have idiopathic hypercalcemia
VERY SMALL percentage will have PHPTH
idiopathic hypercalcemia is a diagnosis….
of exclusion
A cat named Sir Fluffington McWhiskerface comes to you because he is not eating and seems a bit “tired” at home. He is normally very playful and is lying around/sleeping nearly all day for the past few weeks. You do CBC chem and find hypercalcemia. There is no evidence of neoplasia or renal disease. Based on your top dx, what treatment can you offer him?
Alendronate (Fosamax): bisphosphate–>this is a common cancer drug that inhibits osteoclasts and so less calcium is released into the blood
prognosis is guarded to good
what are clinical signs of hypoparathyroidism?
abrupt or intermittent neurologic or neuromuscular changes, often worsened by exercise
tense, nervousness, facial rubbing, cramping, muscle twitching, tremors, stiff or hunched gait, sudden excitement, aggressiveness, change in personality, seizures, tetany
