Hypercalcaemia (and hyperparathyroidism)

Question 1

how is concentration of calcium in the serum regulated?

Answer 1

by the action of PTH and vitamin D on the kidneys, bones and GI tract

Question 2

how does PTH increase serum calcium concentration?

Answer 2

simulation of Ca reabsorption and activation of vit D in the kidney

+ calcium release from bone

Question 3

whats the most active form of vitamin D and what does it increase?

Answer 3

1,25-dihydroxyvitamin D

intestinal calcium absorption

(1st hydration occurs in the liver, 2nd in the kidney)

Question 4

how is calcium transported in the blood?

Answer 4

40% is ionised and physiologically relevant

the rest is bound to albumin + unavailable to tissues

Question 5

what is hypercalcaemia due to?

Answer 5

primary hyperparathyroidism
(+ secondary, tertiary)

malignancy

Question 6

what is tumour-related hypercalcaemia caused by?

Answer 6

the secretion of a peptide with PTH-activity

OR

direct invasion of bone + production of local factors that metabolise Ca

Question 7

primary hyperparathyroidism

Answer 7

0.1% of the population

usually a single parathyroid gland adenoma

Question 8

secondary hyperparathyroidism

Answer 8

physiological compensatory hypertrophy of all the glands in response to prolonged hypocalcaemia e.g. in CKD or vit D deficiency

(Ca2+ is low)

Question 9

tertiary hyperparathyroidism

Answer 9

development of apparently autonomous parathyroid hyperplasia after a longstanding secondary hyperparathyroidism, most often in renal disease

(plasma Ca2+ and PTH are both raised)

Tx: parathyroidectomy

Question 10

clinical features mild hypercalcaemia

Answer 10

often asymptomatic + discovered on biochemical screening

Question 11

clinical features more severe hypercalcaemia

Answer 11

general malaise + depression
bone pain
abd pain
nausea
constipation

Question 12

what is polyuria + nocturia a result of?

Answer 12

calcium deposition in renal tubules

can lead to renal colliculi and CKD

Question 13

clinical features very high hypercalcaemia

Answer 13

dehydration
confusion
clouding of consciousness
risk of cardiac arrest

Question 14

What Ix to confirm mild hypercalcaemia?

Answer 14

several fasting serum calcium + phosphate samples

Question 15

what does serum PTH normal/elevated during hypercalcaemia imply?

Answer 15

primary hyperparathydoism

as PTH should normal only be released if serum Ca is low

Question 16

what excludes primary hyperparathyroidism?

Answer 16

low conc of PTH

Question 17

Mx of severe hypercalcaemia

Answer 17

MEDICAL EMERGENCY!!

IV saline
bisphosphonates after rehydration

Question 18

Mx general

Answer 18

surgical removal of symptomatic parathyroid adenoma

all 4 glands removed if have parathyroid hyperplasia!!

Question 19

what are bisphosphonates

Answer 19

antiresorptive medicines, slow/stop bone breakdown

may prevent the development of osteoporosis.