52 - Disorders of Calcium, phosphate & magnesium

Question 1

Ca is what component in bone

Answer 1

Hydroxyapatite

so it phosphate

Question 2

Physiological important of Mg

Answer 2

Cofactor for ATP
Neuromuscular excitability
Enzymatic function
Regulates ion channels

Question 3

Calcium controlled by

Answer 3

PTH

Vit D and metabolites

Question 4

Calcium relations

Answer 4

GI uptake
Renal clearance
Bone

Question 5

Plasma calcium is in what forms

Answer 5

Ionised (physiologically active)

Bound - inactive, albumin

Complexed - salts, Ca phosphate, calcium citrate

Question 6

What is adjusted calcium

Answer 6

Adj Ca = total Ca + (40-alb) x 0.025

Takes into account bound Ca
Same reference range

Question 7

Acidosis affect of Ca-albumin

Answer 7

Reduces [bound Ca]

Increased [ionised]

Question 8

Alkalosis of Ca-albumin

Answer 8

Increases [bound Ca]

Reduces [ionised Ca]

Question 9

Alkalosis (e.g. hyperventilation) can precipitate … w/ Ca

Answer 9

tetany

Question 10

Hypocalcaemic patients with acidosis - symptoms?

Answer 10

Don’t develop symptoms

Question 11

Ca-PTH loop

Answer 11

Parathyroid uses Mg as cofactor to make PTH which is positive feedback for bone, GI and kidneys to release Ca. Ca then gives -ve feedback to PT glands.

Question 12

PTH does what

Answer 12

Increases Ca turnover with net resorption

Decreases Ca clearance, but, increase phosphate excretion. Vitamin D then increases Ca absorption. Making more plasma Ca

Question 13

Causes of hypocalcaemia

Answer 13

Hypoproteinaemia
Vit D deficiency
HypoPThyroidism
Inadequate intake
Pseudohypoparathyroidism

Question 14

Causes of hypercalaemia

Answer 14

Hyperparathyroidism
Malignancy
Drugs
Vit D excess
Bone disease and immobilisation

Question 15

Distinguishing differential diagnoses using graph - whats on axis

Answer 15

[plasma PTH] vs [serum ionised calcium]

Question 16

Phosphate used

Answer 16

Intracellularly

High energy rxns

Question 17

Phosphate deficiency causes

Answer 17

Hyperparathyroidism
Excess losses
Poor intake

Question 18

Phosphate deficiency - symptoms

Answer 18

Haemolysis, thrombocytopenia + poor granulocyte function

Severe muscle weakness, resp. failure, rhabdomyolysis

Confusion, irritability and coma due to metabolic encephalopathy

Renal dysfunction

Question 19

Phosphate deficiency - treatment

Answer 19

Necessitates changes to IV fluids inc. TPN formulations

Question 20

Hypomagnesaemia associated with

Answer 20

Hypokalaemia
Hyponatraemia
Hypophosataemia
Hypocalcaemia

Question 21

Magnesium depletion - causes

Answer 21

Renal - drugs, hypercalcaemic

GI tract - malnutrition,IV nutrition, diarrhoea, malabsorption

Question 22

Magnesium depletion - effects

Answer 22

Cellular
Biochemical
Endocrine
CVS
CNS
Muscle

Question 23

Tissue Mg status - best predictor is what

Answer 23

Leucocyte Mg - good correlation + predictive value

Muscle Mg - 20% body Mg, important physiologically and requires biopsy