Renal (minerals)

Question 1

What is the function of parathyroid hormone (PTH)?

Answer 1

To increase blood calcium levels and decrease blood phosphorus levels

Question 2

What is the function of calcitonin?

Answer 2

To decrease blood calcium levels and increase blood phosphorus levels

Question 3

What is the function of vitamin D?

Answer 3

To work in the presence of PTH to increase calcium and phosphorus. Calcitriol is the hormonally active metabolite

Question 4

What are the three forms of calcium in the body?

Answer 4

1. Ionized/free (50%)
2. Protein-bound (80% bound to albumin, 20% bound to globulin)
3. Non protein-bound (5-10%)

These three combined are total calcium, which is the value you see on a chemistry panel

Question 5

What marker should calcium be interpreted in conjunction with and why?

Answer 5

Albumin because calcium levels can be affected by hypoalbuminemia (80% of calcium is bound to albumin)

Question 6

Which form of calcium is biologically active and hormonally regulated by PTH, Vitamin D, and calcitonin?

Answer 6

Only the free ionized form (iCa)

Question 7

When would you perform an ionized calcium test?

Answer 7

When we want a more accurate value for calcium in disease states (total calcium includes a large portion of protein-bound calcium, and does not always reflect the true change in the biologically active ionized form)

Question 8

Which three disorders will cause ionized calcium (iCa) to increase?

Answer 8

• Osteolysis (from increased PTH or bone tumors)
• Decreased renal excretion (especially horses!)**
• Increased GI absorption

Question 9

Which three disorders will cause ionized calcium (iCa) to decrease?

Answer 9

• Decreased GI absorption
• Increased renal excretion
• Increased loss in milk (lactation)

Question 10

What are eight causes of hypocalcemia?

Answer 10

1. Primary hypoparathyroidism
2. Hypoalbuminemia
3. Hypovitaminosis D
4. Lactational
5. Nutritional hyperparathyroidism
6. Ethylene glycol toxicity (binds to calcium and increases its excretion)
7. GI disease/protein losing enteropathy (horses and yorkies with PLE)
8. Blister beetle toxicity

Question 11

What are the top three differentials for protein-losing enteropathy?

Answer 11

1. IBD
2. Diffuse intestinal neoplasia
3. Lymphangiectasia

Question 12

What does blister beetle toxicity cause?

Answer 12

Severe hypocalcemia and hypomagnesemia

Question 13

What is a common differential for hypomagnesemia?

Answer 13

Grass tetany in ruminants