Disorders of calcium, phosphate And Magnesium

Question 1

Which two metal ions are found in hydroxyapatite?

Answer 1

Calcium and phosphate.

Question 2

Where is phosphate predominantly found in relation to the cell

Answer 2

Predominantly intracellular

Question 3

What are some of the physiological roles of magnesium?

Answer 3

Cofactor for ATP, neuromuscular excitability, enzymatic function, regulates ion channels, present in bone

Question 4

Where is magnesium store in the body?

Answer 4

Bone

Question 5

What are the four variables which determine metal ion homeostasis?

Answer 5

Intake
Storage
Excretion
Tissue redistribution

Question 6

What are the key factors controlling calcium homeostasis?

Answer 6

Parathyroid hormone and Vitamin D

Question 7

What are the two calcium complexes found in the body?

Answer 7

Calcium phosphate and calcium citrate.

Question 8

What is the reference range for calcium?

Answer 8

2.2-2.6 mmol/L

Question 9

How will adjusted calcium change if albumin is high?

Answer 9

Adjusted calcium will decrease if albumin is high. Inverse relationship between the two.

Question 10

How does pH affect how much calcium is bound to albumin?

Answer 10

Ca ions are positively charged, so compete with H ions. Acidosis reduces the amount of bound Ca.

Alkalosis increases the amount of bound Ca

Question 11

What effect does parathyroid hormone have on calcium levels?

Answer 11

PTH increases calcium concentration in the blood by releasing calcium from bone, stimulates the conversion of vitamin D to active a Vitamin D (1,25 dihydroxycholecalciferol) and enhances reabsorbtion of calcium in distal tubules.

Question 12

What factors decrease vitamin D?

Answer 12

Age, obesity and pale skin.

Question 13

What causes of hypocalcaemia?

Answer 13

Vit D deficiency.
Hypoparathyroidism
Pseudohypoparathyroidism (PTH resistance)
Inadequate intake of calcium
Artifactual; EDTA contamination.

Question 14

How does magnesium cause hypoparathyroidisim?

Answer 14

Magnesium is needed to allow parathyroid hormone to be released. PTH is still synthesised but enzyme needed to release it isn’t functional.

Question 15

What are the causes of hypercalcaemia?

Answer 15

Malignancy
Hyperparathyroidism
Bone disease
Sarcoidosis
Drugs eg diuretics 
VitaminD excess

Question 16

What are the main symptoms of phosphate deficiency?

Answer 16

Muscle fatigue and weakness. Confusion. Renal dysfunction.

Question 17

Why do patients with hyperparathyroidism have low phosphate?

Answer 17

Parathyroid hormone increases kidney excretion of phosphate

Question 18

Other than hyperparathyroidism what else can cause low phosphate?

Answer 18

Low vitamin D

Question 19

What are the causes of hypomagnesaemia?

Answer 19

Malabsorption, malnutrition, diuretic drugs and antibiotics and hypercalcemia.

Question 20

What are th effects of hypomagnesaemia?

Answer 20

Cardiac irritability
Reduced contractility ty 
Tetany
Ataxia
Psychosis
Muscle weakness
Muscle fibrillation

Question 21

What is calcium used for in the body?

Answer 21

Muscle contraction, neuronal excitation, blood clotting, enzyme activity and bone formation