Calcium Disorders Flashcards
What are 4 COMMON causes of hypercalcemia?
Bonus: which is the MOST common?
- lymphosarcoma or lyphoma**
- anal sac adenocarcinoma
- other neoplasia (multiple myeloma)
- renal failure (iCa will be normal)
what are 6 other less common causes of hypercalcemia?
- primary hyperparathyroidism (tumor of PTh Gland –> secretes too much PTH)
- hypoadrenocorticism (inc renal resorption of Ca)
- Vitamin D toxicosis
- granulomatous disease
- bone lysis (Ca stores released)
- lab error (recheck Ca)
In what 3 ways does PTH increase calcium?
When The parathyroid gland senses LOW calcium, the gland secretes PTH.
PTH causes:
1. increased bone resorption of Ca –> releases Ca
2. increased renal Ca resorption and phosphorus excretion
3. increases intestinal calcium and phosphorus absorption
When the parathyroid gland senses hypercalcemia, what is the NORMAL response?
Decrease in PTH
kidneys, bone, and intestines resorb LESS calcium.
When there is disease, this protective mechanism can fail.
What are the 3 forms of calcium?
- ionized (50%)
- protein-bound (albumin; 40%)
- complexed to citrate, phosphate, etc. (10%)
T/F: a hypoalbuminemic patient is likely to have low calcium
true, this is because some calcium is protein bound to albumin.
How can renal failure cause elevated TOTAL calcium, but normal iCa?
total calcium contains 10% calcium complexed to citrate, phosphate, etc. and others bound to albumin
When the kidneys fail, phosphorus increases.
What would you expect the tCa, iCa, P, and PTH to be in a case of primary hyperparathyroidism?
tCa - increased
iCa - increased
PTH - normal/increased
P - DECREASED
What would you expect the tCa, iCa, P, and PTH to be in a case of RENAL secondary hyperparathyroidism?
tCa - norm/inc/dec
iCa - norm/DECREASED
PTH - INCREASED
P - norm/increased
What would you expect the tCa, iCa, P, and PTH to be in a case of hypervitaminosis D?
tCa - INCREASED
iCa - INCREASED
P - INCREASED
Why is hypercalcemia negative for the kidneys? (4 reasons)
- induces nephrogenic diabetes insipidus (impaired collecting tubule response to ADH –> cannot resorb water –> PU/PD –> hyposthenuric)
- Increased medullary blood flow
- Renal arteriolar vasoconstriction (poor perfusion –> ischemia –> AKI)
- Renal dystrophic mineralization (when Ca x P >60)
How does hypercalcemia cause PU/PD?
Reduced tubular function &
Deficiency or impaired response to ADH
What are clinical signs of hypercalcemia?
Clinical signs may not be apparent until Ca > 15.
PU/PD
Anorexia/Hyporexia
Lethargy
Weakness
Cardiac arrhythmias
Seizures/muscle twitching
T/F: if you have a dog with lymphadenomegaly and increased calcium concentrations, it would be a good next step to perform a lymph node aspirate
true
If you do bloodwork on a dog and the total Ca comes back elevated, so you run and PTH and iCa and the PTH comes back LOW, what is your interpretation?
LOW PTH –expected when calcium is high (negative feedback)
If you do bloodwork on a dog and the total Ca comes back elevated, so you run and PTH and iCa and the PTH comes back HIGH, what is your interpretation?
primary hyperparathyroidism (there is neoplasia of the parathyroid gland causing excess PTH and subsequent elevation in calcium)
diagnose based on u/s
What is PTH-independent hypercalcemia?
This is when the tCa and iCa are elevated, but the PTH is LOW.
Common causes of PTH-indepdent hypercalcemia are: lymphosarcoma, anal sac adenocarcinoma, other neoplasias, and renal failure.
Uncommon causes: hypoadrenocorticism, vit D toxicosis, granulomatous disease, bone lysis
After you’ve determined a patient has PTH-independent what diagnostics should/could you run?
Look for causes of PTH independent hypercalcemia (lymphoma, Anal sac adenocarcinoma, multiple myeloma, etc.)
1. thoracic xrays
2. xrays of long bones
3. abdominal u/s
4. rectal exam
5. basal cortisol (if <2, run ACTH stim test)
6. bone marrow aspirate
how would you treat hypercalcemia before it can cause kidney damage? (what is the acute/ER treatment)
ER therapy (be aggressive)
1. IV 0.9% NaCl (causes kidneys to excrete Ca)
2. furosemide (diuresis to excrete Ca)
3. Injectable bisphosphate (stops Ca release from bone)
AVOID THIAZIDES (they cause Ca absorption)
What is the maintenance treatment for hypercalcemia?
- oral corticosteroids
or - oral alendronate (decreases Ca release from bone)
Then treat whatever disease they have that is causing the hypercalcemia (ex. lymphoma –> L-spar, prednisone, chemo CHOP)
