Minerals

Question 1

What makes up the total calcium in the body?

Answer 1

• Free calcium makes up about 50%
• Calcium bound to an anionic protein makes up around 40-45%
• Calcium bound to non-protein anions makes up around 5%

Question 2

Where is PTH secreted from?

Answer 2

It is secreted from chief cells in the parathyroid glands

Question 3

What stimulates the synthesis of PTH release

Answer 3

It is stimulated by low levels of free calcium or low calcitriol (vitamin D)

Question 4

What does PTH promote?

Answer 4

It promotoes increased Ca2+ absorption by the intestine and increased calcium mobilisation from bone

Question 5

What causes increased production of parathyroid hormone?

Answer 5

• primary hyperparathyroidism
• endocrine neoplasia

Question 6

What produces parathyroid hormone related protein?

Answer 6

a number of neoplasms e.g
* apopcrine anal sac adenocarcinomas
* lymphomas (but only a small proportion)
* squamous cell carcinomas (but only a small proportion)

Question 7

What type of blood cell is thought to secrete parathyroid hormone related protein?

Answer 7

Macrophages

Question 8

How is vitamin D formed?

Answer 8

Cholesterol becomes 7-dehydrocholesterol which then goes on to become cholecalciferol

Question 9

In what kind of diseases is an increase in vitamin D expected?

Answer 9

• Granulomatous diseases
• primary hyperpararthyroidism

Question 10

What cells synthesise calcitonin?

Answer 10

It is synthesised by thyroid C cells

Question 11

What is the main function of calcitonin?

Answer 11

acts to reduce the levels of calcium in the blood

Question 12

What are some ways calcitonin decreases blood calcium levels?

Answer 12

• It inhibits osteoclastic activity in the bone
• It inhibits renal tubular absorption of Ca2+ and PO4
  *

Question 13

What is the function of fibroblast growth fcator?

Answer 13

To synthesise osteoblasts and osteocytes

Question 14

What stimulates the synthesis of fibroblast growth factor?

Answer 14

Calcitriol (vitamin D) and increase PO4

Question 15

What can cause hypercalcaemia?

Answer 15

Increased moblisation of calcium from bone
* Increased PTH or PTHrP
* Increased vitamin D activity
* Neoplasia in the bone
* Decreased urinary excretion

Question 16

What can cause hypocalcaemia

Answer 16

• hypoalbuminaemia
• Decreased PTH activity
• Inadequate Calcium mobilisation from the bone
• Excess Urinary excretion of calcium
• Ca2+ binds with diffusable ions

Question 17

What is hypocalcaemia known as in pregnant cows?

Answer 17

Milk fever

Question 18

What is nutritional hypocalcaemia?

Answer 18

When they have a vitamin D deficient diet
The Ca2+/ PO4 ratio is therefore lower than desired

Question 19

What is hyperphosphataemia?

Answer 19

Decreased Urinary PO4 excretion
Phosphate moves from the ICF to the ECF

Question 20

What are three other mechanisms for Hyperphosphataemia?

Answer 20

• Hyperthyroidism in cats
• Lactic acidosis
• Hyperadrenocorticism in dogs

Question 21

What can cause Hypophosphataemia?

Answer 21

• Increased Urinary Phosphate excretion
• Decreased Intestinal Phosphate absorption (prolonged anorexaia or a phosphate deficient diet)
• Shifting of phosphate from the ECF to the ICF

Question 22

How commonly is magnesium measured?

Answer 22

less commonly measured in comparison to calcium and phosphorus
-serum is the preferred sample but heparinised plasma can also be used in some assays
haemolysis or delayed cell separation can also increase magnesium except in cattle

Question 23

What disorder can result in a decreased total magnesium?

Answer 23

hyperproteinaemia

Question 24

Where is magnesium absorbed and excreted?

Answer 24

• absorbed in the GI tract
• excreted in the faeces and the kidneys

Question 25

What can control magnesium?

Answer 25

• 1, 25 DHCC administartion can reduce plasma magnesium
• thyroxine increases excretion of magnesium
• aldosterone promotes increased faecal and urinary excretion of magnesium

Question 26

What can cause hypermagnesia?

Answer 26

• Decreased urinary excretion
• shift from the ICF to ECF
• Increased PTH (milk fever)

Question 27

What can cause hypomagnesaemia?

Answer 27

• Hypoproteinaemia
• inadequate ruminal or intestinal resorption of Mg2+ (prolonged or poor feed intake) grass tetany
• excess urinary excretion of Mg2+ (osmotic diuresis)