Lecture: Calcium

Question 1

Functions of calcium in the body (8)

Answer 1

Structural role
Activator 
Blood caogulation
Skeletal and cardiac muscle contraction 
Nerve impulse transmission 
Milk production
Regulation of membrane ion transport
Cellular secretion

Question 2

Major sources of dietary calcium

Answer 2

Milk and milk products

Question 3

Factors affecting the variability in absorption of calcium from the SI

Answer 3

Concentration in the diet
pH
Presence of activated vitamin D
Parathyroid hormone
High protein Diet
Steatorrhea
Age

Question 4

Storage of calcium in the body

Answer 4

Gut
ECF
Kidney
Bone (highest conc)

Question 5

What 3 forms is calcium present in serum in

Answer 5

Ionised/free (active)
Complexed
Protein bound (inactive)

Question 6

What are blood calcium levels influenced by

Answer 6

Parathyroid hormone
Calcitonin
Vitamin D

Question 7

How many amino acids compose the PTH

Answer 7

84

Question 8

When is PTH released

Answer 8

When ECF calcium is decreased

Question 9

What organs/tissues does PTH act on

Answer 9

Bone, kidney and intestine

Question 10

Describe calcitonin molecule

Answer 10

32 amino acid peptide with one disulphide bond

Question 11

What secretes calcitonin

Answer 11

C cells of the thyroid in response to an increase in ionised calcium

Question 12

Three target tissues for activated vitamin D

Answer 12

Intestine, bone and kidney

Question 13

How much calcium is bound to albumin

Answer 13

50%

Question 14

Non diseases state total serum calcium level

Answer 14

2.4 mmol/L

Question 15

When is binding of calcium to protein decreased/increased

Answer 15

Decreased in acidosis states

Increased in alkalosis states

Question 16

What is normal calcium level required for

Answer 16

Nerve function, membrane permeability and glandular secretion

Question 17

Does PTH glands recognise unbound or bound calcium

Answer 17

Unbound

Question 18

Why is “adjusted calcium used”

Answer 18

So patients with low albumin are not mistaken for being hypocalcaemic
and so
patients with normal calcium low albumin are not missed for being hypercalaemic

Question 19

How to calculate adjusted calcium (mmol/L)

Answer 19

Total calcium + 0.02(47-[albumin])

Question 20

Causes of hypocalcaemia

Answer 20

Hypoparathyroidism
Vitamin D deficiency
Renal disease
Pseudohypoparathyroidism

Question 21

Clinical features of hypocalcaemia

Answer 21

Neurological features such as tingling, tetany and mental changes, cardiovascular signs and cataracts

Question 22

What should adjusted calcium level be

Answer 22

above 2.1 mmol/L

Question 23

What further tests should be done following measuring Ca and albumin to determine if patient is hypocalcaemic

Answer 23

Measure urea and creatinine for renal disease.

Check PTH is appropriate to serum Ca.

Question 24

Treatment for hypocalcaemia

Answer 24

Oral calcium supplements

Question 25

Causes of hypercalcaemia

Answer 25

Primary hyperparathyroidism and hypercalcaemia of malignancy

Question 26

Clinical features of hypercalcaemia

Answer 26

Neurological and psychiatric features such as lethargy, confusion Irritability and depression Gastrointestinal problems such as anorexia, abdominal pain, renal features such as thirst and polyuria Cardiac arrhytmias

Question 27

What does a level of 3.5 mmol/L or greater of adjusted calcium mean

Answer 27

Life threatening and action is required immediately

Question 28

Treatment of hypercalcaemia

Answer 28

Intravenous saline is administered to restore GFR and promote a diuresis Aminohydroxypropylidene diphosphate is treatment of choice in patients with hypercalcemia of malignancy. (inhibits bone reabsorption)

Question 29

Average dietary intake of magnesium

Answer 29

15 mmol per day

Question 30

When is hypermagnesaemia seen

Answer 30

Uncommon but occasionally seen in renal failure

Question 31

Symptoms of hypomagnesaemia

Answer 31

Impaired muscle function such as tetany, hyperirritability, tremor, convulsions and muscle weakness

Question 32

Laboratory diagnosis of hypomagnesaemia

Answer 32

Spectrophotometric with metallochromic indicators, calmagite and methylthymol blue, formazan dye, magon and phosphoazo III

Question 33

At what level of magnesium conc. might benefit from magnesium therapy

Answer 33

< 0.7 mmol/L

Question 34

How to detect intracellular magnesium concentration when Mg is within reference range

Answer 34

Research procedure NMRspectro-scopy to detect free MG 2+ inside cells

Question 35

What can magnesium supplements cause

Answer 35

Diarrhoea

Question 36

What is phosphate attached to

Answer 36

Inside cells mostly attached to lipids and proteins

Question 37

Where is most of the bodys phosphate

Answer 37

In bone

Question 38

How is control of ECF phosphate concentration achieved

Answer 38

By the kidney where tubular reabsorption is reduced by PTH

Question 39

Normal phosphate concentration (monohydrogen phosphate and dihydrogen phosphate)

Answer 39

0.8 -1.4 mmol/L

Question 40

Causes of hyperphosphateaemia

Answer 40

Renal failure Hypoparathyroidism Haemolysis Pseudohypoparathyroidism

Question 41

Causes of hypophosphataemia

Answer 41

``` Hyperparathyroidism Congenital defects of tubular phosphate reabsotpion Ingestion of non-absorbabke antacids Treatment of diabetic ketoacidosis Sever dietary deficiency. ```