Clinical Chemistry 3 - Divalent Ions

Question 1

What is the overall effect of PTH?

Answer 1

To increase calcium and decrease phosphate concentrations

Question 2

The secretion of PTH from the parathyroid glands is triggered by what?

Answer 2

Low serum calcium

Question 3

What effect does PTH have on bone?

Answer 3

Increases osteoclast activity to cause calcium and phosphate release from bone

Question 4

What happens to phosphate once it has been taken out of bone?

Answer 4

It is excreted by the kidneys

Question 5

What effect does PTH have on the kidneys?

Answer 5

Increased calcium reabsorption and decreased phosphate reabsorption

Question 6

In addition to altering reabsorption of calcium and phosphate, what other action does PTH have at the level of the kidneys?

Answer 6

Increases production of calcitriol

Question 7

Where is vitamin D hydroxylated?

Answer 7

First in the liver, then in the kidneys

Question 8

1, 25-dihydroxy-vitamin D3 is the active form of vitamin D. What is this known as?

Answer 8

Calcitriol

Question 9

Calcitriol production is stimulated by what?

Answer 9

PTH release

Question 10

What is the major action of calcitriol?

Answer 10

Increased calcium and phosphate absorption from the gut

Question 11

In addition to the gut, calcitriol also causes calcium and phosphate to be absorbed from where?

Answer 11

Kidneys

Question 12

What effect does calcitriol have on bone?

Answer 12

Increased bone turnover

Question 13

What effect does calcitriol have on PTH?

Answer 13

Inhibition of its release

Question 14

Disordered regulation of calcitriol underlies which clinical condition?

Answer 14

Familial normocalcaemic hypercalciuria

Question 15

Familial normocalcaemic hypercalciuria is a major cause of the formation of which type of renal stone?

Answer 15

Calcium oxalate

Question 16

Where is calcitonin produced?

Answer 16

C-cells (parafollicular cells) of the thyroid

Question 17

When does calcitonin have an effect on calcium metabolism?

Answer 17

When there is hypercalcaemia

Question 18

How does calcitonin decrease serum calcium levels in response to hypercalcaemia?

Answer 18

Reduces osteoclastic activity

Question 19

Calcitonin levels can be used as a tumour marker for what?

Answer 19

Medullary thyroid cancer

Question 20

A low level of which electrolyte prevents PTH release, and therefore may cause hypocalcaemia?

Answer 20

Magnesium

Question 21

‘Stones, bones, groans and psychic moans’ classically describes the symptoms of which electrolyte imbalance?

Answer 21

Hypercalcaemia

Question 22

What will an ECG of hypercalcaemia show?

Answer 22

Shortened QT interval

Question 23

What are the two most common causes of hypercalcaemia?

Answer 23

Primary hyperparathyroidism and hypercalcaemia of malignancy

Question 24

What are some reasons that malignancies may cause hypercalcaemia?

Answer 24

Bony metastases, myeloma, PTH-related-peptide release

Question 25

What happens to phosphate and ALP levels in hypercalcaemia of malignancy?

Answer 25

Increased

Question 26

If a patient has a calcium level > 3.5mmol/l and is symptomatic, how should they be treated?

Answer 26

Saline and bisphosphonates

Question 27

What are some mild features of hypocalcaemia?

Answer 27

Cramps and peri-oral numbness

Question 28

What are some severe features of hypocalcaemia?

Answer 28

Carpo-pedal spasm, laryngospasm, seizures

Question 29

Trousseau’s and Chvostek’s signs indicate what electrolyte abnormality?

Answer 29

Hypocalcaemia

Question 30

What does Trousseau’s sign show?

Answer 30

On inflating a BP cuff, the wrist and fingers draw together

Question 31

What does Chvostek’s sign show?

Answer 31

The corner of the mouth twitches when the facial nerve is tapped over the parotid gland

Question 32

What does an ECG of hypocalcaemia show?

Answer 32

Prolonged QT interval

Question 33

What happens to phosphate levels in patients with hypocalcaemia due to CKD, hypoparathyroidism, hypomagesaemia or vitamin D deficiency?

Answer 33

High

Question 34

What are some causes of hypocalcaemia with a low or normal phosphate level?

Answer 34

Osteomalacia, respiratory alkalosis, over-hydration, pancreatitis

Question 35

How should mild symptoms of hypocalcaemia be treated?

Answer 35

Oral calcium supplements

Question 36

In hypocalcaemia due to CKD, supplementation of what else as well as calcium may be necessary?

Answer 36

Vitamin D

Question 37

How should severe symptoms of hypocalcaemia be treated?

Answer 37

10mls 10% calcium gluconate IV over 30 minutes (and repeated as necessary)

Question 38

Hyperphosphataemia is most commonly caused by what?

Answer 38

CKD

Question 39

How is hypophosphataemia treated?

Answer 39

Oral or IV phosphate supplementation

Question 40

IV phosphate supplementation should never be given to which patients?

Answer 40

Those who are hypercalcaemic or oliguric

Question 41

Plasma concentrations of magnesium tend to follow those of which other ions?

Answer 41

Calcium and potassium

Question 42

What is the main cause of hypermagnesaemia?

Answer 42

CKD

Question 43

If hypermagnesaemia is severe, what kind of symptoms does it cause?

Answer 43

Symptoms due to CNS and respiratory depression

Question 44

Other than hypokalaemia, what other electrolyte abnormality also enhances digoxin toxicity?

Answer 44

Hypomagnesaemia

Question 45

How does a zinc deficiency usually occur?

Answer 45

Parenteral nutrition or very poor diet

Question 46

What are some symptoms of zinc deficiency?

Answer 46

Alopecia, dermatitis, night blindness and diarrhoea