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calcium dysregulation Flashcards

1
Q

what hormones are responsible for calcium and phosphate regulation

A

vit d
parathyroid hormone
calcitonin

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2
Q

what hormones increase serum calcium and phosphate

A

vit d - synthesised in skin

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

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3
Q

what hormone decreases serum calcium and phosphate

A

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

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4
Q

how do we replenish vit d in our bodies

A

main way is via sunshine

and diet

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5
Q

what are the first 3 steps in vit d synthesis

A

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

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6
Q

what are the two essential hydroxylation steps in vit d synthesis

A

25 hydroxylase in liver to make 25(oh)cholecalciferol

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

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7
Q

what do we call the active form of vit d

A

calcitriol

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8
Q

what is a good indicator of body vit d status

A

serum oh vitamin d

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9
Q

how does calcitriol regulate its own synthesis

A

decreases transcription of 1 alpha hydroxylase

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10
Q

what are the effects of calcitriol on the bone

A

increases osteoblast activity - bone formation

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11
Q

what are the effects of calcitriol on the kidneys

A

increased calcium and phosphate reabsorption

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12
Q

what are the effects of calcitriol on the gut

A

increased calcium and phosphate absorption

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13
Q

what are the effects of pth on bone

A

increase calcium resorption from bone - osteoclast activity

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14
Q

what are the effects of pth on the kidneys

A

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

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15
Q

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

A

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

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16
Q

what is the main focus of parathyroid hormone

A

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

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17
Q

what is the hormone fgf23 made by ?

A

osteocytes

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18
Q

what is role of fgf23

A

regulate phosphate levels

19
Q

what can high levels of fgf23 cause

A

low levels of phosphate

20
Q

what does fgf23 do to in proximal convoluted tubule

A

inhibits sodium phosphate co transporter

forces phosphate not to be reabsorbed

21
Q

what is another action of fgf 23

A

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

22
Q

what does hypocalcaemia cause

A

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

23
Q

what are the signs and symptoms go hypocalcaemia

A 
parathesia
convulsions
arrythmias
tetany
CATS go numb
24
Q

what are two signs we can look out for in hypocalcaemia

A

chvosteks sign - facial parathesia

trosseaus sign - carpopedal spasm

25
Q

how do we check for chvosteks sign

A

tap zygomatic arch for facial nerve

contraction on that side of neck

26
Q

how to check for trosseaus sign

A

tight blood pressure cuff

arm contracts and can’t relax

27
Q

what are the causes of hypocalcaemia related to low pth

A 
= hypoparathyroidism
could be from neck surgery
autoimmune
magnesium deficiency (needed for pth secretions)
congenital - agenesis , rare
28
Q

what are the causes of hypocalcaemia related to low vit d

A

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

29
Q

what does hypercalcaemia cause

A

reduced neuronal excitability - atonal muscles

why - calcium blocks sodium channels preventing action

30
Q

effects of hypercalcaemia on kidneys

A

renal effects - kidney stones

renal colic

31
Q

what are the effects of hyper cal on gi

A 
gi effects - anorexia
nausea
dyspepsia
constipation
pancreatitis
32
Q

what are the effects of HYPERCALCAEMIA on the cns

A 
cons effects - fatigue
depression
impaired concentration
impaired mentation
coma if >3mmol/l
33
Q

what is a way to remember symptoms of hypercalcaemia

A

stones, abdominal moans, psychic groans

34
Q

what is the most common cause of hypercalcaemia

A

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

35
Q

what are some other causes of hypercalcaemia

A

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

36
Q

biochem of primary hyperparathyroidism

A

high calcium
low phosphate - increased renal excretion
high pth

37
Q

what is the treatment of primary hyperparathy…

A

parathyroidectomy

38
Q

risks of untreated hyperparathyroidism

A

osteoporosis
stones
psychological impact

39
Q

what is secondary hyperparathyroidism

A

calcium is low!!

normal physiological response to low calcium

40
Q

causes of secondary hyperparathyroidism

A

vit d deficiency diet, reduced sunlight

less common - renal failure

41
Q

treatment of secondary hyperparathyroidism

A

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

42
Q

what is tertiary hyperparathyroidism

A

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

43
Q

treatment for tertiary hyper-parathy…

A

parathyroidectomy

brs2 (65 decks)

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