Hypercalcemia

Question 1

What 2 values are indicative of hypercalcemia on blood work?

Answer 1

1. serum total calcium >12 mg/dL
2. serum ionized calcium >1.4 mmol/L

Question 2

What 3 hormones control calcium levels in the serum? How do they work?

Answer 2

1. PTH - increases Ca and P mobilization from bone and promotes phosphate excretion and calcium retention by the kidneys
2. calcitriol - increases Ca and P absorption from intestines
3. calcitonin - reduces Ca levels by inhibition of osteoclastic bone resorption

Question 3

When are clinical signs of hypercalcemia seen? What are 2 classic signs? What else can be seen?

Answer 3

> 15 mg/dL (>18 mg/dL causes major debilitation)

1. PU/PD
2. seizures, muscle tremors

• anorexia, depression, weakness
• vomiting
• constipation
• arrhythmias

Question 4

What are 10 major differential diagnoses for hypercalcemia?

Answer 4

1. granulomatous disease / growing young dogs
2. osteolytic disease
3. spurious - lipemic or post-prandial blood samples, lab error, hemolysis
4. hyperparathyroidism (primary)
5. drugs
6. Addison’s disease
7. renal failure
8. nutritional
9. idiopathic (cats!)
10. tumors

GOSH DARN IT

Question 5

What are 3 nutritional causes of hypercalcemia?

Answer 5

1. hypervitaminosis D - drugs, cholecalciferol rodenticide, poisonous plants
2. hypervitaminosis A
3. excess Ca

Question 6

What drugs may cause hypercalcemia?

Answer 6

• thiazides
• calcium-containing phosphate binders

Question 7

What are the 2 major classifications of neoplastic causes of hypercalcemia?

Answer 7

1. humoral hypercalcemia of malignancy - lymphoma, AGASACA
2. bone osteolysis - multiple myeloma, lymphoma

Question 8

What are 4 parts to a good workup and diagnosis of hypercalcemia?

Answer 8

1. thorough history and PE - rectal, lymph node and mammary chain palpation, orthopedic exam
2. CBC, chem, UA - assess BUN/CREAT for renal function, electrolytes (Na:K ratio), globulins (increased = suggestive of myeloma/lymphoma
3. diagnostic imaging - thoracic radiographs for hilar lymphadenopathy, granulomatous pulmonary disease, or lytic bone lesions
4. additional testing depending on degree of suspicion of hypoadrenocorticism, hyperparathyroidism, or neoplasia –> ACTH stim, U/S or CT/MRI to assess parathyroid gland, PTH-rP levels

Question 9

What is the best treatment for hypercalcemia?

Answer 9

identify and address underlying etiology

Question 10

What are 6 options for treating symptoms of hypercalcemia?

Answer 10

1. IV fluid diuresis with 0.9% NaCl
2. Furosemide - promotes calciuresis, only give to hydrated patients (avoid thiazides!)
3. Prednisone/Dexamethasone - promote calciuresis and decrease bone resorption and intestinal absorption of calcium
4. bisphosphonates - inhibit osteoclasts
5. calcitonin
6. sodium bicarbonate - decreases ionized calcium (emergency treatment)

Question 11

What symptomatic treatment of hypercalcemia should be avoided if diagnosis is unknown?

Answer 11

prednisone and dexamethasone - administration to a possible lymphoma patient can hamper diagnoses and decrease effectiveness of eventual treatment