calcium dysregulation

Question 1

what hormones are responsible for calcium and phosphate regulation

Answer 1

vit d
parathyroid hormone
calcitonin

Question 2

what hormones increase serum calcium and phosphate

Answer 2

vit d - synthesised in skin

Pth - secreted by parathyroid glands - main regulators of homeostasis via actions on kidney, bone and gut

Question 3

what hormone decreases serum calcium and phosphate

Answer 3

calcitonin - secreted by parafollicular cells
- reduce ca acutely
no neg effect if cells removed e.g in thyroidectomy

Question 4

how do we replenish vit d in our bodies

Answer 4

main way is via sunshine

and diet

Question 5

what are the first 3 steps in vit d synthesis

Answer 5

uvb absorbed by skin
7 dehydrocholesterol converted into pre vit d3
pre vit d converted into vit d3 in skin
travels in blood

Question 6

what are the two essential hydroxylation steps in vit d synthesis

Answer 6

25 hydroxylase in liver to make 25(oh)cholecalciferol

1 alpha hydroxylase in kidney - becomes 1,25 oh2 cholecalciferol

Question 7

what do we call the active form of vit d

Answer 7

calcitriol

Question 8

what is a good indicator of body vit d status

Answer 8

serum oh vitamin d

Question 9

how does calcitriol regulate its own synthesis

Answer 9

decreases transcription of 1 alpha hydroxylase

Question 10

what are the effects of calcitriol on the bone

Answer 10

increases osteoblast activity - bone formation

Question 11

what are the effects of calcitriol on the kidneys

Answer 11

increased calcium and phosphate reabsorption

Question 12

what are the effects of calcitriol on the gut

Answer 12

increased calcium and phosphate absorption

Question 13

what are the effects of pth on bone

Answer 13

increase calcium resorption from bone - osteoclast activity

Question 14

what are the effects of pth on the kidneys

Answer 14

increased calcium reabsorption
increased phosphate excretion
increase production of 1 alpha hydroxylase activity

Question 15

what is the effect of pth causing increase of 1 alpha hydroxylase activity

Answer 15

synthesis of calcitriol which acts on gut increasing calcium and phosphate absorption in gut

Question 16

what is the main focus of parathyroid hormone

Answer 16

increase plasma calcium
through its actions on bone and kidney
and indirect action on gut

Question 17

what is the hormone fgf23 made by ?

Answer 17

osteocytes

Question 18

what is role of fgf23

Answer 18

regulate phosphate levels

Question 19

what can high levels of fgf23 cause

Answer 19

low levels of phosphate

Question 20

what does fgf23 do to in proximal convoluted tubule

Answer 20

inhibits sodium phosphate co transporter

forces phosphate not to be reabsorbed

Question 21

what is another action of fgf 23

Answer 21

it inhibits calcitriol formation - leading to less phosphate reabsorption from gut.

Question 22

what does hypocalcaemia cause

Answer 22

it sensitises excitable tissues - causing muscle cramps tetany and tingling(parathesia).

Question 23

what are the signs and symptoms go hypocalcaemia

Answer 23

parathesia
convulsions
arrythmias
tetany
CATS go numb

Question 24

what are two signs we can look out for in hypocalcaemia

Answer 24

chvosteks sign - facial parathesia

trosseaus sign - carpopedal spasm

Question 25

how do we check for chvosteks sign

Answer 25

tap zygomatic arch for facial nerve | contraction on that side of neck

Question 26

how to check for trosseaus sign

Answer 26

tight blood pressure cuff | arm contracts and can't relax

Question 27

what are the causes of hypocalcaemia related to low pth

Answer 27

``` = hypoparathyroidism could be from neck surgery autoimmune magnesium deficiency (needed for pth secretions) congenital - agenesis , rare ```

Question 28

what are the causes of hypocalcaemia related to low vit d

Answer 28

deficiency - diet, uv light, malabsorption, impaired production - renal failure (1 alpha hydroxylation)

Question 29

what does hypercalcaemia cause

Answer 29

reduced neuronal excitability - atonal muscles | why - calcium blocks sodium channels preventing action

Question 30

effects of hypercalcaemia on kidneys

Answer 30

renal effects - kidney stones | renal colic

Question 31

what are the effects of hyper cal on gi

Answer 31

``` gi effects - anorexia nausea dyspepsia constipation pancreatitis ```

Question 32

what are the effects of HYPERCALCAEMIA on the cns

Answer 32

``` cons effects - fatigue depression impaired concentration impaired mentation coma if >3mmol/l ```

Question 33

what is a way to remember symptoms of hypercalcaemia

Answer 33

stones, abdominal moans, psychic groans

Question 34

what is the most common cause of hypercalcaemia

Answer 34

primary hyperparathyroidism - too much pth -usually due to parathyroid gland adenoma not sensitive to neg feedback therefore high pth and high calcium

Question 35

what are some other causes of hypercalcaemia

Answer 35

malignancies- bony metastases produce local factors to activate osteoclasts certain cancers secrete pth related peptide that acts on pth receptors vit d excess e.g vit d supplements

Question 36

biochem of primary hyperparathyroidism

Answer 36

high calcium low phosphate - increased renal excretion high pth

Question 37

what is the treatment of primary hyperparathy...

Answer 37

parathyroidectomy

Question 38

risks of untreated hyperparathyroidism

Answer 38

osteoporosis stones psychological impact

Question 39

what is secondary hyperparathyroidism

Answer 39

calcium is low!! | normal physiological response to low calcium

Question 40

causes of secondary hyperparathyroidism

Answer 40

vit d deficiency diet, reduced sunlight | less common - renal failure

Question 41

treatment of secondary hyperparathyroidism

Answer 41

vit d replacement ergocalciferol - d2 cholecalciferol - d3 if have renal failure - alfacalcidol - active version

Question 42

what is tertiary hyperparathyroidism

Answer 42

chronic renal failure rare cannot make vit d for long period of time glands cells hyperplasia to compensate cells can't switched off

Question 43

treatment for tertiary hyper-parathy...

Answer 43

parathyroidectomy