Calcium dysregulation

Question 1

which hormones act to increase serum calcium

Answer 1

vitamin D (calcitriol)
parathyroid hormone

Question 2

which hormones act to decrease serum calcium

Answer 2

Calcitonin

Question 3

what are the sources of calcitriol?

Answer 3

synthesised in skin, diet

Question 4

what are the sources of parathyroid hormone

Answer 4

parathyroid gland

Question 5

what are the sources of calcitonin

Answer 5

thyroid parafollicular cells

Question 6

what are the main sources of calcium in the body?

Answer 6

bones, gut, kidney

Question 7

what is the difference between vitamin D2 and D3

Answer 7

D2 from diet (ergo)

D3 from skin (chole)

Question 8

which enzymes are essential for vitamin D synthesis

Answer 8

25-hydroxylase (liver)

1-a-hydroxylase (kidney)

Question 9

name all the physiological effects of calcitriol

Answer 9

increases calcium and phosphate reabsorption in kidneys
increases calcium and phosphate absorption in gut
increases osteoblast activity

Question 10

name all the physiological effects of PTH

Answer 10

increased calcium reabsorption in kidney, increased excretion of phosphate, increased 1ah action (vit D synthesis)
increases calcium and phosphate absorption in the gut
increases osteoclast activity

Question 11

where is FGF23 made

Answer 11

by osteocytes

Question 12

what is the main role of FGF23

Answer 12

prevents kidney reabsorption of phosphate

inhibits Vit D synthesis (via reduced activity of 1-a-hydroxylase)

Question 13

what is FGF23s MOA

Answer 13

inhibits Na/PO4 transporter in proximal tubule of kidney (more excretion of PO4)
inhibits calcitriol synthesis (for less PO4 absorption in gut)

Question 14

what are the two signs of hypocalcaemia

Answer 14

Chvosteks sign (facial paresthesia)
Trousseaus sign (carpopedal spasm)

Question 15

what are the symptoms of hypocalcaemia

Answer 15

CATs go numb

convulsions, arrhythmias, tetany, paraesthesia

Question 16

what are the two major causes of hypocalcaemia

Answer 16

due to low PTH

due to low Vit D

Question 17

what are some causes of low PTH causing hypocalcaemia

Answer 17

neck surgery
autoimmunity
magnesium deficiency
congenital agenesis of Pt gland

Question 18

what are some causes of low calcitriol causing hypocalcaemia?

Answer 18

deficiency due to diet, lack of UV (darker skin more prone), malabsorption, impaired production (renal failure)

Question 19

what are the signs of hypercalcaemia

Answer 19

stones, (abominal) moans and psychic groans

Nephrocalcinosis; anorexia, nausea, dyspepsia, constipation and pancreatitis; fatigue, depression and impaired concentration

Question 20

what are the symptoms of hypercalcaemia

Answer 20

nephrocalcinosis, kidney stones, renal colic
anorexia, nausea, dyspepsia, constipation, pancreatitis
fatigue, depression, impaired concentration, altered mentation, coma

Question 21

what is the most common cause of hypercalcaemia

Answer 21

parathyroid gland adenoma

Question 22

what are the main causes of hypercalcaemia

Answer 22

primary hyperparathyroidism
malignancy
vit D excess

Question 23

how can malignancy cause hypercalcaemia?

Answer 23

bony metastases produce local factors to activate osteoclasts
or certain cancers secrete PTH-related peptide which acts on PTH receptors

Question 24

what would be the blood results for primary hyperparathyroidism

Answer 24

high calcium, low phosphate, high PTH

Question 25

what is the cause of primary hyperparathyroidism?

Answer 25

parathyroid adenoma - autonomous secretion of PTH

Question 26

how do you treat primary hyperparathyroidism?

Answer 26

parathyroidectomy

Question 27

what are the long term risks of primary hyperparathyroidism?

Answer 27

osteoporosis
renal calculi
mental and mood deficits

Question 28

what is secondary hyperparathyroidism?

Answer 28

normal physiological response to chronically low calcium

Question 29

what are the blood results for secondary hyperparathyroidism?

Answer 29

low/norm Ca2+

high PTH

Question 30

what is the most common cause of secondary hyperparathyroidism?

Answer 30

Vit D/calcitriol deficiency

Question 31

what are the causes of secondary hyperparathyroidism?

Answer 31

Vit D deficiency by diet or reduced sunlight

renal failure

Question 32

how do you treat someone with secondary parathyroidism who has normal renal function?

Answer 32

vitamin D replacements - usually D3

Question 33

how do you treat someone with secondary hyperparathyroidism in renal failure?

Answer 33

give Alfacalcidiol - 1-a-hydroxycholecalciferol

Question 34

why do treatments differ for 2o hyperparathyroidism depending on renal function?

Answer 34

renal failure patients have inadequate 1a-hydroxylation so can’t activate 25hydroxy vit D preparations like those with normal renal function

Question 35

what is tertiary hyperparathyroidism?

Answer 35

chronically low Ca2+ in the context of chronic renal failure and prolonged calcitriol deficiency, where one gland produces PTH independent of any other factors

Question 36

what are the consequences of tertiary hyperparathyroidism?

Answer 36

PTH increases, PT gland enlarges (hyperplasia)

autonomous PTH secretion causes hypercalcaemia

Question 37

how is tertiary hyperparathyroidism treated?

Answer 37

parathyroidectomy

Question 38

how does high calcium affect the nerves

Answer 38

Calcium ions block sodium ion influx so there is less membrane excitability

Question 39

how does low calcium affect the nerves

Answer 39

low Ca2+ allows more sodium ion influx so there is increased membrane excitability