Calcium Dysregulation

Question 1

Which 2 molecules increase serum calcium levels?

Answer 1

1. Vitamin D
2. Parathyroid Hormone (PTH)

Question 2

Which hormone is responsible for decreasing serum calcium levels?

Answer 2

Calcitonin

Question 3

What are the 2 sources of vitamin D?

Answer 3

1. Synthesised in skin
2. Intake via diet

Question 4

Where is PTH secreted from?

Answer 4

Parathyroid glands

Question 5

Where is calcitonin secreted from?

Answer 5

Parathyroid follicular cells

Question 6

What is the active form of vitamin D called?

Answer 6

Calcitriol or 1,25(OH)2 cholecalciferol

Question 7

Which form of vitamin D is found in diet?

Answer 7

Vitamin D2

Question 8

What induces the production of vitamin D in skin?

Answer 8

UVB from sunlight

Question 9

Which form of vitamin D is produced in the skin?

Answer 9

Vitamin D3

Question 10

Which enzyme turns vitamin D3 into 25-OH cholecalciferol?

Answer 10

25-hydroxylase

Question 11

Where is 25-hydroxylase found?

Answer 11

Liver

Question 12

What is a good indicator of body vitamin D status?

Answer 12

25-OH vitamin D (25-OH cholecalciferol)

Question 13

Which enzyme turns 25-OH cholecalciferol into calcitriol?

Answer 13

1-alpha-hydroxylase

Question 14

How does calcitriol regulate its own synthesis?

Answer 14

Decreasing transcription of 1-alpha-hydroxylase

Question 15

What are the physiological effects of calcitriol?

Answer 15

• Increased Ca2+ and (PO4)3- absorption from intestines
• Increased Ca2+ and (PO4)3- reabsorption from kidneys

Question 16

How do the physiological effects of calcitriol influence bones?

Answer 16

Increased Ca2+ and (PO4)3- provide building blocks for bones

Question 17

What are the actions of PTH?

Answer 17

• Increased Ca2+ resorption from bones
• Increased Ca2+ reabsorption from kidneys
• Increased (PO4)3+ excretion from kidneys
• Increased 1-alpha-hydroxylase activity

Question 18

Which transport protein does PTH act on to increase phosphate excretion?

Answer 18

Na+/(PO4)3- co-transporter

Question 19

Where is Na+/(PO4)3- co-transporter found within the kidneys?

Answer 19

Cuboidal epithelia of proximal tubule

Question 20

What other factor acts on sodium/phospate co-transporter in the kidneys?

Answer 20

Fibroblast Growth Factor-23 (FGF23)

Question 21

What is the action of FGF23?

Answer 21

• Increased phosphate excretion
• Reduced 1-alpha-hydroxylase activity

Question 22

What are the symptoms of hypocalcaemia?

Answer 22

CATs go numb
* Convulsions
* Arrythmia
* Tetany
* Paraesthesia (hands, feet, mouth, lip)

Question 23

What is paraesthesia?

Answer 23

Tingling sensation and numbness

Question 24

What is the sign indicated by facial paraesthesia called?

Answer 24

Chvostek’s Sign

Question 25

How is Chvostek's sign observed?

Answer 25

Facial twitch or spasm observed upon tapping the zygomatic arch (cheekbone)

Question 26

What is the sign indicated by carpopedal spasm?

Answer 26

Trousseau's Sign

Question 27

How is Trousseau's sign observed?

Answer 27

Spasm of hands and fingers upon inflating a blood pressure cuff on the arm

Question 28

What are the 2 main causes of hypocalcaemia?

Answer 28

1. Low PTH levels (hypoparathyroidism) 2. Low Vitamin D levels

Question 29

What are the causes of hypoparathyroidism?

Answer 29

* Neck surgery * Autoimmune * Congenital (agenesis)

Question 30

What are the causes of low vitamin D levels?

Answer 30

* Poor diet * Malabsorption * Lack of UV light * Impaired production (renal failure)

Question 31

What are the signs of hypercalcaemia?

Answer 31

1. Stones 2. Abdominal moans 3. Psychic groans

Question 32

What are the symptoms related to stones?

Answer 32

Renal Effects * Nephrocalcinosis - kidney stones, renal colic

Question 33

What are the symptoms related to abdominal moans?

Answer 33

GI effects * Anorexia * Nausea * Dyspepsia * Constipation * Pancreatitis

Question 34

What are the symptoms related to psychic groans?

Answer 34

CNS Effects * Fatigue * Depression * Impaired concentration * Altered mentation * Coma (usually >3 mmol/L)

Question 35

What are the 3 main causes of hypercalcaemia?

Answer 35

* Primary hyperparathyroidism * Malignancy * Excess Vitamin D

Question 36

What causes primary hyperparathyroidism?

Answer 36

Parathyroid gland adenoma

Question 37

How can malignancy cause hypercalcaemia?

Answer 37

Certain cancers (like squamous cell cancer) secrete peptides that mimic PTH

Question 38

Which one of the 3 main causes of hypercalcaemia is rare?

Answer 38

Excess Vitamin D