Calcium dysregulation

Question 1

what does FGF23 do?

Answer 1

• Derived from osteocytes
• Phosphate regulation by kidney reabsorption by inhibiting these transporters
• Inhibits calcitriol to lower phosphate

Question 2

What are hypocalcaemia symptoms?

Answer 2

Paraesthesia (hands, mouth, feet , lips)
Convulsions
Arrhythmias
Tetany

Question 3

What is hypocalcaemia?

Answer 3

Sensitises excitable tissues; muscle cramps, tetany, tingling

Question 4

What are the signs of hypocalcaemia?

Answer 4

• Chvosteks’ sign – facial paresthesia *zygomatic arch of the facial nerve
• Trousseau’s sign – carpopedal spasm

Question 5

How does low PTH cause hypocalcaemia?

Answer 5

Hypoparathyroidism due to:

• Neck surgery
• Autoimmune
• Magensium defiency
• Congenital

Question 6

How does low Vitamin cause hypocalcaemia?

Answer 6

Deficiency :

• Diet
• UV light
• malabsorption
• Impaired production ( renal failure )

Question 7

What are the signs of hypercalcaemia?

Answer 7

‘Stones, abdominal moans and psychic groans’

Reduced neuronal excitability – atonal muscles

Question 8

What does it mean by ‘stones’ in hyperCa?

Answer 8

renal effects

Nephrocalcinosis – kidney stones, renal colic

Question 9

What does it mean by ‘Abdominal moans’ in hyperCa?

Answer 9

GI effects

Anorexia, nausea, dyspepsia, constipation, pancreatitis

Question 10

What does it mean by ‘Psychic groans’ in hyperCa?

Answer 10

CNS effects

Fatigue, depression, impaired concentration, altered mentation, coma (usually >3mmol/L)

Question 11

what are the causes of hypercalcaemia?

Answer 11

Primary hyperparathyroidism:

• parathyroid gland adenoma
• no negative feedback so notice high PTH but high Calcium

Malignancy:

• Bony metastases produce local factors to activate osteoclasts
• Cancers e.g. squamous cell carcinomas secrete PTH-related peptide that acts atPTH receptors

Vit D excess : rare

Question 12

What is the biochemistry of hyperparathyroidism?

Answer 12

High calcium
Low phosphate ( due to increased renal excretion- inhibition of Na+/PO43- transporter )
High PTH

Question 13

What can occur if hyperparathyroidism is not treated?

Answer 13

• Osteoporosis
• Renal Calculi
• Psychological impact e.g. mental function, mood

Question 14

What is the treatment choice for primary hyperparathyroidism?

Answer 14

Parathyroidectomy

Question 15

What is the biochemistry of secondary hyperparathyroidism?

Answer 15

Low Calcium
PTH high secondary to low calcium

Normal physiological response to hypocalcaemia

Question 16

What are the causes of secondary hyperparathyroidusm?

Answer 16

Calcium deficiency due to vit D deficiency

less common : renal failure causing calitriol to not be made

Question 17

How to treat secondary hyperparathyroidism?

Answer 17

Vit D replacement:

• 25 hydroxy vitaminD
  body then creates calcitriol itself

Question 18

How to treat secondary hyperparathyroidism? in px wil renal failure?

Answer 18

• inadequate 1a hydroxylation, so can’t activate 25 hydroxy vitamin D preparations
  Give Alfacalcidol -
  1alpha hydroxycholecalciferol

Question 19

What is tertiary hyperparathyroidism?

Answer 19

Chronic renal failure
Chronic vit D deficiency
Decreased calcium

Causes excessive PTH release cause of chronic nature and is hard to turn off

Question 20

How to treat tertiary hyperparathyroidism?

Answer 20

parathyroidectomy = will need to remove the gland to control ( have 4 glands so remove 1 )

Question 21

What diagnostic approach should you use when looking at hypercalaemia?

Answer 21

When you see a px with high calcium always look at PTH

Question 22

Biochemistry due to malignancy hypercalaemia?

Answer 22

High calcium (hypercalcaemia)
Low/suppressed PTH

Question 23

What if patient with hypercalcaemia has raised PTH?

Answer 23

• has raised PTH, the diagnosis is hyperparathyroidism
• Primary hyperparathyroidism if renal function is normal (eg parathyroid adenoma)
• Tertiary hyperparathyroidism (all 4 glands enlarged – hyperplastic) if chronic renal failure

Question 24

How is Vit D measured?

Answer 24

measured as 25 (OH) vitamin D
Calcitriol (1,25 dihydroxy vitamin D) is very difficult to measure

In low calcium PTH will be high secondary to low calcium