Calcium hormones Flashcards
List the main roles of calcium in the body?
5th most abundant element in body,
used in meuromuscular excitability, muscle contraction, bone stegth, second messenger and co-enzyme, blood coagulation
How is calcium stored and intook by th body?
50% is unbound in blood, rest is bound to plasma protein
a lot of Ca in the bone
a lot in Gi tract but not absorbed (85%)-rest is ditributed between blood, bones, cells and kindeys as urine-metabolism mostly targets reabosption
Where are the parathyroid gland located? And what are parafolicular cells?
Parathyroid glands (4) are located in each gland of the thyroid (right and left) and at the top and bottom of each. They release parathyroid hormone (PTH) when Ca sensors activate (low Ca)-aim to increase it In the thyroid, around follicules, parafollicular cells release calcitonin which decreases body Ca
Describe parathyroid hormone (parathromone) and its main actions in body)
PTH is synthesises as pre-proPTH -84aas as PTH
Act on GCPR -cAMP and PLC
Acts on bones-stimulate osteoclast (rankL increase) and decrease osteoblast-increase Ca available
Also acts on Kindeys-increase Ca intake by glomerulus, increases PO4 excretion, and increase synthesys of 1,25 OH2D3 (Vit D3-calcitrol)-which acts on small intestine to increase Ca absorption and PO4
Describe PTH regulation and feedback loop
Decreased plasma Ca, Catcholamines increase parathyroid release of PTH
Resulting Calcitriol and increases plasma Ca have negative feedback on parathyroid gland PTH release
How is Calcitrol synthesised, onptained and made active?
Diet/from cholesterol (with UV) can get Cholecalciferol (Vit D3)
In liver, synthesised to 25 OH D3
And in LIVER, made into calcitrol (1.25 OH2 D3). PTH increases activity of the 1a hydrolase (that does that reaction)
What are the main effects of calcitrol?
Acts on kidney to increase Ca and PO4 reabsotption, and same in GI
It also increases ostroblast activity-tries to reduce what PTH is doing to bone
What is Fibroblast growth factor 23, why does it matter in Ca metabolism?
Ca metabolism is linked with PO4 regulation-Calitriol and Pi in body can uptrgulate production of FGF23 (made by ostoblasts)-activate PTH release (if high PO4, usually low Ca)
PTH inhibits of Na/po4 cotransporter (use Na gradient)
FGF23 also does that-and is increases by calcitrol through osteoblast stimulation
The main function of FGF23 seems to be regulation of phosphate concentration in plasma. FGF23 is secreted by osteocytes in response to elevated calcitriol. FGF23 acts on the kidneys, where it decreases the expression of NPT2, a sodium-phosphate cotransporter in the proximal tubule.[8] Thus, FGF23 decreases the reabsorption and increases excretion of phosphate. FGF23 may also suppress 1-alpha-hydroxylase, reducing its ability to activate vitamin D and subsequently impairing calcium absorption
What is Calcitonin? what are its main actions in the body?
Synthesised as pro-procalitronin-32aa as hormone
GCPR-cAMP and PLC
increases plasma Ca and gastrin increae parafollicular release of calitronin-inhibits osteoclast, and increase urinary exretion of Ca, Na and PO4
But has very lmited activity-body trizes to increase Ca rather than reduce
What are 3 endocrine causes of hypocalceamia? give a few exemple of sings aused by Ca deficiency
Hypoparathyroidism, pseudohypoparathyroidism, Vitamin D deficiency
causes tetany such as trousseaus signs -craned hand)
Chvosteks signs
What are the main causes of hypoparathyroidsim?
thyroid diseases (addisons), not having one at all,radiotherapy consequences or hypomagnesia (low magnesium) Associated with low Ca, Low PTH and high PO4
What are the main cause and symptoms of pseudohypoparathyroidsim?
Resitance of PTH by target organ-thought to be caused by defecive G proteins
Features include-short stature, round face, low IQ, calcification and bone abnormality, associated endocrine disorder (hypothyroidism)
associated with High PTH, high PO and low Ca
What are the main symptoms of vitamin D deficiency?
Rickets in children, osteomalacia in adults
clinical-calcification of bones resulting in short bones, fractures mostly in adults
Coincides with low Ca and PO4 as well because dont reabsorb by GI as much
What are the 3 main endocrine causes of hypercalceamia?
Primary, (secondary), tertiary hyperparathyroidism, vit D Toxicosis (so much its toxic)
Explain the mechanism and symptoms of Primary, (secondary) and tertiary hyperparathyroidism. Also list the main symtoms associtaed with these 3 diseases?
Primary-adenoma of aprathyroid glands-produce PTH and no negative feedback-bone brittle, high Ca
Secondary-Low plasma CA/excessive PTH -eg:renal failure-Ca keeps exiting because not reabsorbed
Tertiary-after prolonged secondary-Parathyroid gland start becoming autonomous and dont respond to regulation-constant push of PTH
Because all cause PTH excess-Kindeys aborb lot of Ca, less PO (polyuria, kindet stones, nepthrocalcinosis), and icrease calcitriol
Gi tract gets acid and ulcers
bone-lesion, rarefaction, fractures
causes clubbing of fingers-erosion of bone in terminal phalanges
