Session 5 - Kalcium and the Cidney (intentional, promise)

Question 1

Give five functions of Calcium

Answer 1

• Muscle contraction
  
  • Inactivation/activation of enzymes
  • Nerve conduction
  • Exocytosis
  • Hormone secretion
  • Haemostasis

Question 2

What is the physiologically active from of Ca2+?

Answer 2

• Ionised form

Question 3

Give the three forms in which Ca2+ is found in the body

Answer 3

• Free ionised species
  
  • Protein bound
  • Complexed

Question 4

How much of dietary calcium is absorbed?

Answer 4

• 20-40% is absorbed (25mmol)

Question 5

When does calcium absorption increase? (3)

Answer 5

• Growing children
  
  • Pregnancy
  • Lactation

Question 6

How much calcium do the kidney filter per day?

Answer 6

• 250mmol

Question 7

How much of the body’s calcium reservoir is found in the ECF?

Answer 7

• 1%

Question 8

What chemical is responsible for the absorption of calcium from the gut?

Answer 8

• 1,25 - OH 2D control

Question 9

Where is the majority of calcium reabsorption in the kidney?

Answer 9

• 65% reabsorbed in proximal tubule
  
  • 20-25% recovered in ascending loop of henle
  • 10% recovered in DCT under control of PTH

Question 10

What is the standard 24hr urinary calcium excretion?

Answer 10

• <10 mmol

Question 11

How much calcium filtered by kidney per day?

Answer 11

250 mmol

Question 12

Give the actions of PTH

Answer 12

• Increases reabsorption in kidney
  
  • Increases breakdown of bone

Converts calciferol to calcitriol in kidney

Question 13

What is the inactive form of Calcitriol called?

Answer 13

Calciferol

Question 14

What are the actions of calcitriol?

Answer 14

• Increase breakdown of bone
  
  • Increase reabsorption in kidney

Increase absorption of calcium from gut

Question 15

How is vitamin d2 produced?

Answer 15

• By gut

Question 16

How is vitamin d3 produced?

Answer 16

• By skin

Question 17

How does vitamin D become calciferol?

Answer 17

• Hydroxylation in the liver

Question 18

When does calciferol become calcitriol?

Answer 18

• After 2nd hydroxylation

Question 19

How is Calcium release regulated?

Answer 19

• Negative feed back to parathyroid gland
  
  • Gq receptor inhibit PTH release
  • Reduce further calcium absorption

Question 20

What are the three major causes of hypercalcaemia?

Answer 20

• Primary hyperparathyroidism
  
  • Haemtological malignancies
  • Non-haematological malignancies

Question 21

How do malignancies cause hypercalcaemia?

Answer 21

• PTHrp released

* Does not convert calciferol to calcitriol

Question 22

Give four systems that hypercalcaemia causes symptoms in

Answer 22

• Gastrointestinal
  
  • Cardiovascular
  • Renal
  • CNS

Question 23

Give four gastrointestinal symptoms of hypercalcaemia

Answer 23

• Anorexia
  
  • Nausea/Vomiting
  • Constipation

Question 24

Give three cardiovascular consequences of hypercalcaemia

Answer 24

• HypertensionShortened QT

* Enhanced sensitivity to digoxin

Question 25

Give three renal consequences of hypercalcaemia

Answer 25

* Polyuria * Polydipsia * Nephrocalcinosis

Question 26

Give three cognitive effects of hypercalcaemia on the CNS

Answer 26

* Cognitive difficulties * Apathy * depression

Question 27

Outline treatments for hypercalcaemia

Answer 27

General measures • Hydration - Increase Ca2+ excretion • Loop diuretics - Increase Ca2+ excretion Specific measures • Bisphosphonates - Inhibit breakdown of bone • Calcitonin - Opposes the action of PTH Treat underlying condition

Question 28

What percentage of people will develop kidney stones in their life?

Answer 28

* 20% mean | * 5-10% of women

Question 29

What is the most common form of kidney stone?

Answer 29

• 70-80% made of calcium

Question 30

What factors are involved in the formation of kidney stones?

Answer 30

* Low urine volume * Hypercalcuria Low urin pH

Question 31

What does the mechanism of stone formation involve?

Answer 31

• Super-saturation of urine with calcium oxalate

Question 32

What does conservative management of kidney stones involve?

Answer 32

* Increasing fluid intake * Restricting dieatary oxalate and sodium * Restrict calcium and animal protein

Question 33

What calcium conc do we want to measure in the blood?

Answer 33

• Ionised calcium

Question 34

What are the problems with measuring ionised calcium?

Answer 34

Degrades quickly

Question 35

What hormone is responsible for calcium absorption from the gut?

Answer 35

Calcitriol (a derivative of vitamin D)

Question 36

How is excess vitamin D stored?

Answer 36

• Converted to 24,25 - (OH)2 vitamin D Inert

Question 37

Why do people with HIV get vitamin D deficiency?

Answer 37

• Anti-retroviral treatment induces liver enzymes to break down vitamin D

Question 38

Where is calcium reabsorbed in the most part?

Answer 38

* PCT - 65% | * TAL - 25%

Question 39

What three things regulate calcium reabsorption in the kidney?

Answer 39

* PTH * Vitamin D * Plasma Ca2+ levels

Question 40

What can be used to treat hypercalcaemia that acts on the kidney?

Answer 40

• Loop diuretics which inhibit Ca2+ reabsorption

Question 41

Whyshould thiazide not be used in hypercalcaemia?

Answer 41

• Increases Ca2+ reabsorptio in kidney

Question 42

What percent of men get renal stones?

Answer 42

• 20%

Question 43

What is the main type of renal stone?

Answer 43

• Calcium

Question 44

Give three types of renal stone other than calcium

Answer 44

* Magnesium Ammonium Phosphate * Urate * Cystine

Question 45

What is gout?

Answer 45

* Too much alcohol * Alcohol competes with urate in kidney * Urate accumulated in tissues

Question 46

Give five promoters of kidney stone formation?

Answer 46

* Urine supersaturation with calcium oxalate * Low ionic strength * Low citrate * Magnesium * Low pH

Question 47

What is nephrolithiasis?

Answer 47

• Calculi in the kidney

Question 48

What is the classic presentation of kidney stones?

Answer 48

* Loin to groin pain * Renal colic * Hydronephrosis