7. Regulation and disorders of calcium and phosphate metabolism (PTH, calcitonin, D-hormone)

Question 1

Give the total plasma Ca²⁺ concentration

Answer 1

2.5mmol/l

Question 2

Give the divisions of Ca²⁺ concentration in the plasma

Answer 2

• Ionised form - 40% (1.2mmol/l)
• Albumin bound - 50%
• In complex molecules - 10%

Question 3

List the functions of Ca²⁺

Answer 3

• Structure of bones and teeth
• Co-factor for blood clotting
• Muscle contraction
• Hormone: Secretive function of cell receptors

Question 4

List the determining factors of the distribution of calcium

Answer 4

• Demand
• Intake
• Blood phosphate content
• The function of Parathyroid C-cells
• Alkalosis
• Acidosis

Question 5

How does demand affect calcium distribution?

Answer 5

Related to body productivity:

• Egg laying
• Lactation

Question 6

How does intake affect calcium distribution?

Answer 6

• Grains + Grasses = Low Ca²⁺
• Clover + alfalfa = High in Ca²⁺
  
  • ​Overfeeding of alfalfa → Underfunction of the parathyroid gland
  • Postpartum → Decrease of Ca²⁺ = Milk fever

Question 7

How does blood phosphate affect calcium distribution?

Answer 7

Blood phosphate is inversely related to the blood calcium level

Question 8

How does parathyroid C-cell function affect calcium distribution?

Answer 8

1. C-cells release PTH (responsible for Ca²⁺ conc.)
2. Parathyroid gland stimulates osteoclasts to break down bone
3. Calcium release → ↑ Blood Ca²⁺

Question 9

Parathyroid C-cell function has an indirect effect on…

Answer 9

• Vitamin D - Responsible for Ca²⁺ and PO₄^3- absorption
• Hypoalbuminaemia → Causes decrease in total Ca²⁺

Question 10

How does alkalosis affect calcium distribution?

Answer 10

• Causes an increase in protein-bound calcium
• This occurs at the expense of ionised calcium

Question 11

How does acidosis affect calcium distribution?

Answer 11

• Causes an increase in ionised calcium
• This occurs at the expense of protein-bound calcium

Question 12

Give the factors regulating calcium and phosphate absorption

Answer 12

• Demand of the organism
• Age
• Body weight
• Intestinal peristalsis
• Intestinal circulatory disorders
• Fat, Mg, F, Phytin
• Protein

Question 13

How does demand of the organism affect the regulation of calcium and phosphate absorption?

Answer 13

The greater the need, the more efficient absorption is

Question 14

How does ageing affect the regulation of calcium and phosphate absorption?

Answer 14

↑ Age = ↓ Absorption

Question 15

How does body weight affect the regulation of calcium and phosphate absorption?

Answer 15

↑ Body weight = ↓ Absorption

Question 16

How does intestinal peristalsis affect the regulation of calcium and phosphate absorption?

Answer 16

↑ Intestinal peristalsis = ↓ Absorption

Question 17

How do intestinal circulatory disorders affect the regulation of calcium and phosphate absorption?

Answer 17

↑ intestinal circulatory disorders = ↓ Absorption

Question 18

How does Fat, Mg, F and Phytin intake affect the regulation of calcium and phosphate absorption?

Answer 18

↑ Fat, Mg, F and Phytin = ↓ Absorption

Question 19

How does protein intake affect the regulation of calcium and phosphate absorption?

Answer 19

↑ Protein intake = ↑ Absorption

Question 20

List the hormones responsible for phosphate and calcium regulation

Answer 20

• PTH
• Calcitonin
• D-Hormone

Question 21

How does PTH regulate phosphate and calcium?

Answer 21

PTH release:

• ↑ Kidney P → ↓Plasma P
• P + C is mobilised from bones → ↑ Plasma P + C
• Doesn’t result in P concentration change due to compensation
• Results in ↑ plasma C

Question 22

How does calcitonin regulate phosphate and calcium?

Answer 22

• ↑ renal excretion → ↓ Plasma P level
• Causes ↓ mobilisation of C from the bones → ↓ plasma C
• Results in ↓ plasma C + P

Question 23

How does D-hormone regulate phosphate and calcium?

Answer 23

• Facilitates intestinal C, P and Mg absorption
• Stimulates several transport proteins
• Provides proper balance of C + P to support mineralisation
• Improved utilisation of phytin

Question 24

In the kidney, vitamin D is converted to…

Answer 24

D-hormone

Question 25

List the causes of Vitamin D-deficiency

Answer 25

• Genetic defects in vitamin D receptor
• Severe liver/kidney disease
• Insufficient exposure to sunlight
• Improper intake

Question 26

Give the consequences of D-hormone deficiency

Answer 26

• Osteoporosis
• Rickets
• Osteomalacia
• Osteoarthritis
• Abnormalities of PTH
• High BP