Calcium Disorders

Question 1

What are 4 COMMON causes of hypercalcemia?

Bonus: which is the MOST common?

Answer 1

1. lymphosarcoma or lyphoma**
2. anal sac adenocarcinoma
3. other neoplasia (multiple myeloma)
4. renal failure (iCa will be normal)

Question 2

what are 6 other less common causes of hypercalcemia?

Answer 2

1. primary hyperparathyroidism (tumor of PTh Gland –> secretes too much PTH)
2. hypoadrenocorticism (inc renal resorption of Ca)
3. Vitamin D toxicosis
4. granulomatous disease
5. bone lysis (Ca stores released)
6. lab error (recheck Ca)

Question 3

In what 3 ways does PTH increase calcium?

Answer 3

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

Question 4

When the parathyroid gland senses hypercalcemia, what is the NORMAL response?

Answer 4

Decrease in PTH
kidneys, bone, and intestines resorb LESS calcium.
When there is disease, this protective mechanism can fail.

Question 5

What are the 3 forms of calcium?

Answer 5

1. ionized (50%)
2. protein-bound (albumin; 40%)
3. complexed to citrate, phosphate, etc. (10%)

Question 6

T/F: a hypoalbuminemic patient is likely to have low calcium

Answer 6

true, this is because some calcium is protein bound to albumin.

Question 7

How can renal failure cause elevated TOTAL calcium, but normal iCa?

Answer 7

total calcium contains 10% calcium complexed to citrate, phosphate, etc. and others bound to albumin
When the kidneys fail, phosphorus increases.

Question 8

What would you expect the tCa, iCa, P, and PTH to be in a case of primary hyperparathyroidism?

Answer 8

tCa - increased
iCa - increased
PTH - normal/increased
P - DECREASED

Question 9

What would you expect the tCa, iCa, P, and PTH to be in a case of RENAL secondary hyperparathyroidism?

Answer 9

tCa - norm/inc/dec
iCa - norm/DECREASED
PTH - INCREASED
P - norm/increased

Question 10

What would you expect the tCa, iCa, P, and PTH to be in a case of hypervitaminosis D?

Answer 10

tCa - INCREASED
iCa - INCREASED
P - INCREASED

Question 11

Why is hypercalcemia negative for the kidneys? (4 reasons)

Answer 11

1. induces nephrogenic diabetes insipidus (impaired collecting tubule response to ADH –> cannot resorb water –> PU/PD –> hyposthenuric)
2. Increased medullary blood flow
3. Renal arteriolar vasoconstriction (poor perfusion –> ischemia –> AKI)
4. Renal dystrophic mineralization (when Ca x P >60)

Question 12

How does hypercalcemia cause PU/PD?

Answer 12

Reduced tubular function &
Deficiency or impaired response to ADH

Question 13

What are clinical signs of hypercalcemia?

Answer 13

Clinical signs may not be apparent until Ca > 15.

PU/PD
Anorexia/Hyporexia
Lethargy
Weakness
Cardiac arrhythmias
Seizures/muscle twitching

Question 14

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

Answer 14

true

Question 15

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?

Answer 15

LOW PTH –expected when calcium is high (negative feedback)

Question 16

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?

Answer 16

primary hyperparathyroidism (there is neoplasia of the parathyroid gland causing excess PTH and subsequent elevation in calcium)

diagnose based on u/s

Question 17

What is PTH-independent hypercalcemia?

Answer 17

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

Question 18

After you’ve determined a patient has PTH-independent what diagnostics should/could you run?

Answer 18

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

Question 19

how would you treat hypercalcemia before it can cause kidney damage? (what is the acute/ER treatment)

Answer 19

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)

Question 20

What is the maintenance treatment for hypercalcemia?

Answer 20

1. oral corticosteroids
   or
2. 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)