Hypercalcemia and hypocalcemic disorders in dogs and cats

Question 1

function of calcium in the body

Answer 1

Intracellular second messenger involved in signalling systems
Nerve conduction and neuromuscular transmission
Coagulation
Muscle contraction
Membrane stability

Question 2

3 main hormone systems in control of Ca

Answer 2

parathyroid hormone (PTH)
vitamin D + its metabolites
calcitonin

Question 3

PTH - when is it secreted

Answer 3

secreted by the chief cells of the parathyroid gland in response to decr serum levels of ionised calcium

Question 4

PTH - effects

Answer 4

kidneys - decr Ca excretion and incr calcitriol production
bone - incr Ca resorption
GIT - incr Ca absorption by effects on calcitriol production
incr phosphate excretion through enhanced phosphaturia - hyperparathyroidism tends to develop nephrocalcinosis.

Question 5

PTHrP (parathyroid hormone related peptide)

Answer 5

PTH like factor excreted by some neoplastic cells + causes hypercalcemia with malignancy.

Question 6

Vitamin D and its metabolites

Answer 6

steroid hormone
The biologically active metabolite is calcitriol
Vitamin D synthesised in skin or ingested in the diet
converted in the liver and kidneys to the active for.

Question 7

calcitrol effects

Answer 7

incr serum Ca by incr GI absorption of Ca

facilitates renal reabsoprtion of Ca + mobilises Ca + phosphorus from bone

Question 8

Calcitonin

Answer 8

secreted in response to hypercalcemia by the C cells of the thyroid gland
physiological effects are minor

Question 9

Measurement of calcium

Answer 9

Clinically total serum calcium is most commonly measured parameter
ionised calcium is the physiologically significant value controlled by homeostatic mechanisms

Question 10

measuring Ca with serum albumin conc

Answer 10

common cause of a total hypercalcemia is an incr albumin conce seen with dehydration.
total calcium is incr this is d/t incr in bound fraction + is of no physiological significance
patient with low serum albumin may have a normal total Ca but has incr in ionised calcium that is potentially life-threatening

Question 11

hypercalcaemia - clinical signs

Answer 11

often vague - can be mistaken for natural aging
PU/PD, anorexia, dehydration, weakness/lethargy and vomiting
severe less common signs - facial pruritis, oral discomfort, cardiac arrhythmias, seizures/twitching, acute renal failure and death.

Question 12

hypercalcaemia - effects on kidney

Answer 12

interferes with kidney’s ability to conc urine - patients may be dehydrated with a pre-renal azotaemia but still have urine with a relatively low specific gravity
exacerbated d/t high Ca also causes vasoconstriction of the afferent glomerular arteriole, decr in GFR + azotemia.

Question 13

hypercalcaemia - causes - non pathologic

Answer 13

Young animals
Lab error
Spurious (lipaemia)

Question 14

hypercalcaemia - causes - transient incosequential

Answer 14

Hypoadrenococrticism
Haemoconcentration
Hyperproteinaemia

Question 15

hypercalcaemia - causes - pathologic

Answer 15

Malignancy (esp lymphoma, anal sac adenocarcinoma)
Primary hyperparathyroidism 
Renal failure
Hypervitaminosis D
Granulomatous disease (fungal infection, lungworm)
Toxic 
Skeletal lesions
Idiopathic (cats)

Question 16

hypercalcaemia - most common causes

Answer 16

neoplasia

primary hyperparathyroidism, chronic renal failure, granulomatous inflammatory disorders and hypoadrenocorticism

Question 17

Primary hyperparathryroidism - cause

Answer 17

parathyroid adenoma of the parathyroid glands

nodule is non-palpable but readily ultrasonographically demonstrable

Question 18

Evaluation of patient with hypercalcemia

Answer 18

PE including rectal examination
Haematology, biochemistry, UA
Aspiration of masses/enlarged lymph nodes
Imaging of thorax and abdomen to assess for neoplasia
Bone marrow aspirate
Ultrasound of neck
ACTH stimulation test
Test for other granulomatous (infectious) disease –dependent on geographical location
PTH/PTHrP levels
Calcitriol measurement

Question 19

hypercalcaemia - treatment of underlying disease

Answer 19

Chemotherapy for some neoplastic diseases
surgery for neoplastic disease and primary hyperparathyroidism
Anti-fungals/antiparastitics in granulomaotus disease

Question 20

hypercalcaemia - treatment without definitive diagnosis

Answer 20

Diuresis with 0.9%NaCl
Bisphosphonates therapy e.g. palmidronate
Calcitonin
Furosemide 
Peritoneal dialysis

Question 21

why not to use glucocorticoids`

Answer 21

lower serum Ca but mask underlying disease - diagnosis more difficult

Question 22

long term effect of hyercalcaemia

Answer 22

renal failure secondary to soft tissue mineralisation

more likely if the phosphorus level is also elevated

Question 23

hypocalcaemia - clinical signs

Answer 23

muscle tremors/cramps, stiff gait, behavioural change, panting, hyperthermia tachycardia, hypotension, death

Question 24

hypocalcaemia - causes

Answer 24

Chronic renal failure
Eclampsia (pregnancy disorder)
Acute pancreatitis
Iatrogenic (post thyroidectomy/parathyroidectomy, post blood transfusion)
Ethylene glycol toxicity
Intestinal malabsorption
Primary hypoparathyroidism

Question 25

hypocalcaemia - treatment - acute

Answer 25

IV 10% calcium gluconate

Question 26

hypocalcaemia - treatment - chronic

Answer 26

Oral calcium supplementation
vitamin D metabolite
Ergocalciferol (cheap but long half-life)
Dihydrotachysterol (intermediate price, intermediate half-life
Calctriol (most expensive but shortest half life)