Calcium balance Flashcards
What are the 2 main endocrine players in ca metabolis?
PTH-parathyroid hormone and Vitamin D
PTH-increase serum calcium
Vit D-increase serum Ca
Where are the 2 main site of action of PTH for Ca? What is another ones of its effect?
Bone and Kidney
Increase resorbption of Bone for Ca, and increase resoption of Ca via the Kidney
Increases Activation of Vitamin D in the liver to cholcecalfiferol-and (activated in the Kidney (to calcitriol)-increase CA and PO absorb from gut
What is the relation between Phosphate and Calcium? What hormones are involved in Phosphate balance?
Sodium is reabsorbed in Kidney at the same time as Phosphate
PTH inhbits this co-transporter-lower serum PO because cant reabsorb if PTH high (low Ca)
FGF23 also inhibits the PO transporter in the Kidney -and also acts on reducing calcitriol to reduce PO reabsorption (from the GUT)
How is PTH regulated by the parathyroid cells?
Calcium sensing receptor outside the cells-when serum Ca is high, activate the receptor and INHIBITS PTH release
When serum Ca is low, no Ca bind and PTH is release (not inhbited)-and re-increase serum CA
What is the pathway of Vitamin D synthesis?
Can take from the diet-but not so much (in the form of ergocalciferol (cholecalciferol equivalent)
Or, UV activation of 7-dehydroxycholesterol in skin to cholecalciferol
Both can be made in liver to 25-OH D3 (still inactive)
Then in the Kidney, 25-OH D3 can be made to 1,25 OH D3-Calcitriol (active Vit D)-this is done by 1a hydroxylase-controlled by PTH
What are the main effects of calcitriol?
Active vit D causes Ca and reabsoption in gut, Increase Renal reabsoption, fortification of Ca in bones and decrease PTH - the automatically off switch (decrease 1a hydroxylase activity)
What are the 5 main reasons for Vit D deficiency?
malabsortion or dietary problems-celiac disease, bad diet, etc-lowers ergocalciferol
Low sunshine-lowers natural cholecalciferol (glass isnt good)
Liver diseases-cant transform the VitD2/3 into 25-OH D3-cant make the first step/storage
Kidney disease-cant make the active form of Vit D
Rarely-Receptors arent working properly
Where are the main symptoms of Hyper and Hypo calceamia found? Why?
Around nerves and muscles
Na influx is improtant to generate the action potential-
In hypercalceamia, with high extracellualr Ca, Na flux is reduced and excitability is reduced. In hypocacleamia, other way around, more Na can enter-hyperexcitable
What is a mnemonic for Hypocalceamia symptoms? and what are they?
PCAT- P-parasthesia (hands,mouth, feet, etc)-pins and needles C-Convulstions A-arrythmias T-tetany
CATs go Numb
Overall-increase activity-mucle cramps, tetany, etc)
Remember Chvoztecs signs-tap facial nerve below zygomatic bone-whole face twitchs
Trousseau’s sign-when inflate a blood pressure cuff, crane like hand tensed msucle
What are two signs seen in hypocalceamia?
Chvoztecs signs-tap facial nerve below zygomatic bone-whole face twitchs-neuromuscluar irritability
Trousseau’s sign-when inflate a blood pressure cuff, crane like hand tensed msucle
What are the 4 main causes of hypocalceamia?
Vitamind D deficiency
Low PTH-neck surgery, AUTOIMMUNE, Magnesium deficiency (needed to release PTH)
PTH resistance-pseudoparathyroidism
Renal failure-no 1a hydroxylase
What is a mnemonic for Hypercalceamia symptoms? and what are they?
Stones, bones, abdnominal moans and psyhic groans
Reduced neuronal excitability
Stones-kidney stones-polyuria and thirst-more Ca filtered out, and Kidney stones-and if left untreated-kidney failure
Abdominal moans-GI effects-Anorexia, dyspesia, contipation, pancreatities (overall just a very slow gut-as it isnt being excited)
Psychic groans-CNS effects-depression/low mood/coma/altered mind-not to be underestimated
Why would you have High calcium (4 main causes)
main ones: Primary hyperthyroidism or cancer
Some tumours-release a PTH-like peptide
Some tumours reach bone-cause major bone turnover-and increase serum CA
Primary hyperthyroidism
Rarer-Vitamin D excess
What are the diagnostical approach to high Ca?
If you find high Ca, must see a PTH and Vit D to understand
If Ca is high, appropriate is to see low PTH
In primary hyperparathyroidism-Ca is up but PTH is also up-independent-find high Ca, high/normal (an unsupressed) PTH and LOW PO
if tumour increase bone turnover, Ca is high, but PTH is working fine-so Ca high, PTH LOW
Why is vitamin D deficiency bad?
needed to minealise bone-in children makes rickets-very obious as bones arent growing proper-bendy soft bones, in adults-osteomalacia-more like fracture, slow healing,
