Physiology of hypercalcaemia

Question 1

Describe calcium homeostasis

Answer 1

PTH:
- PTH increases when calcium is low
- PTH decreases when calcium is high

Active vitamin D (calcitriol):
- activated in kidney
- promoted by PTH
- Inhibited by FGF-3

Question 2

What are the causes of hypercalcaemia?

Answer 2

Increased PTH activity - primary hyperparathyroidism
Activity of PTH-like substances - humoral hypercalcaemia of malignancy (parathyroid hormone related peptide - PTHrP)
Increased Vit D activity
Osteolysis

Question 3

What is PTHrP produced by?

Answer 3

cartilage
bone
muscle
epithelium
CNS
specific tumours

Question 4

What are principal differentials for parathyroid dependent hypercalcaemia (primary hyperparathyroidism)

Answer 4

Parathyroid adenoma
Parathyroid adenocarcinoma
Parathyroid hyperplasia
Calcium sensor defect

Question 5

What are the principal differentials for parathyroid independent hypercalcaemia?

Answer 5

Humoral hypercalcaemia of malignancy
Vit D excess
Granulomatous disease
Osteolysis
Feline idiopathic hypercalcaemia
Raisin toxicity
Angiostrongylus

Question 6

What are the causes of hypercalcaemia? (HARD IONS)

Answer 6

Question 7

What are the causes of total hyper calcaemia in dogs?

Answer 7

Question 8

What are the causes of total hypercalcaemia in cats?

Answer 8

Question 9

What are the clinical signs of hypercalcaemia?

Answer 9

PU/PD
Weakness
Depression
Mental dullness
Anorexia
Vomiting
Constipation
Muscle twitching
Shivering
Seizures
Bradycardia
Cardiac arrhythmias

Question 10

Why does hyper Ca cause PU/PD?

Answer 10

antagonism of ADH => PU/PD via secondary nephrogenic diabetes insipidus

Question 11

Why does hyperCa cause weakness, depression and mental dullness?

Answer 11

Depressed excitability of muscular and nervous tissue

Question 12

Why does hyperCa cause anorexia, vomiting and constipation?

Answer 12

decrease in excitability of GI smooth muscle
Direct CNS effect

Question 13

Why does hyperCa cause muscle twitching, shivering and seizures?

Answer 13

cerebral microthrombi
vasospasm

Question 14

Why does hyperCa cause bradycardia and cardiac arrhythmias?

Answer 14

increased contractility
Decreased myocardial excitability

Question 15

How can hyperCa cause soft tissue mineralisation

Answer 15

If P is also high they precipitate and cause soft tissue mineralisation

Question 16

What can be measured to assess for hyperCa?

Answer 16

Ionised Ca
Albumin
Phosphorous (identify if PTH or Vit D related)
Chloride
Urea and creatinine
Na:K ratio

Question 17

What is the cause of hypercalcaemia?

Answer 17

Question 18

How are PTH and ionised Ca used to diagnose the cause of hyperCa?

Answer 18

Question 19

Describe how renal or nutritional secondary hyperparathyroidism causes hypercalcaemia and the biochemistry associated

Answer 19

Renal dysfunction or bad diet => high serum phosphorous
PTH excreted to lower P levels => increased iCa
P is not excreted so Ca + P precipitate => soft tissue mineralisation
Biochemistry:
- high PTH
- low iCa
- high total Ca

Question 19

What are the clinical features of hypervitaminosis D

Answer 19

Increased Ca x P product => soft tissue mineralisation
Vomiting, anorexia, lethargy
Acute PU/PD
Acute renal failure
Dysrhythmias
Seizures
Death

Question 20

Fill in the table on the biochemistry seen in different causes of hyperCa

Answer 20

Question 21

what is the cause of hyperCa here?

Answer 21

Primary hyperparathyroidism - parathyroid tumour

Question 22

what is the cause of hyperCa here?

Answer 22

Non-parathyroid tumour releasing PTHrP => increased iCa which => low PTH by negative feedback

Question 23

What is the cause of hyper Ca here?

Answer 23

Vitamin d related or PTHrP been lost in transport