Calcium Phosphate Flashcards
Responses of physiologic system to levels of Ca and P are in regards to the levels here:
blood
Net drive of Ca and P into bone:
growing
What hormones help regulate the net loss and gain of bone?
Estrogens and testosterone
These cells regulate Ca levels in blood:
C cells, production and release of calcitonin (thyroid tissues)
True or False? Calcitonin is very important physiologically.
F
Cells that make parathyroid hormone:
chief cells
Procedure for hyperthyroidism:
thyroidectomy
Issues with thyroid removal
reverse hyperthroidism state and create an iatrogenic issue in Ca and P balance because parathyroid tissue was accidentally cut out as well
primary action of calcitonin:
Excrete Ca and P
Calcitonin is more important for what animal?
fish
Drug for postmenopausal women at risk for osteoporosis:
calcitonin, decreases osteoclasts, prevents osteoporosis
3 important hormones for Ca and P homeostasis:
parathyroid hormone, vitamin D, calcitonin
True or False? Bone is a fast responder to changes in Ca and P levels.
F. slow
True or False? Direction of Ca and P movement is the same for the gut and bone.
T
Differential regulation of Calcium levels vs. P levels occurs here:
kidney, some passive and some active channels
What affects Ca and P regulation at the level of the kidney
parathyroid hormone
Low blood calcium:
take up in the gastrointestinal or excrete less, reabsorb more from filtrate.
Functions of parathyroid hormones
to increase plasma calcium levels
High calcium levels affect parathyroid hormone levels in this way:
inhibit parathyroid hormone secretion
Low calcium levels:
parathyroid hormone release and calcium reabsorption in kidney
___% of calcium that enters kidney is reabsorbed
98
how much Ca and P is taken in via the diet daily?
1gm
What % of filtered load …
90% of filtered load
Reabsorption via calcium transporter in the distal tubule
active transport stimulated via parathyroid hormone (increases calcium reabsorption)
Proximal tubule, hydroxylases
hormone stimulate proximal tubule to activate vit D (steroid) goes to gut to increase absorption of both Ca and P, stimulates production of calbindin (calcium binding in the duodenum, transport into the blood)
Target of Vit D:
gut to increases Ca and P(more passive for P)
2 ways parathyroid hormone increase Ca and P levels:
directly increases reabsorption of calcium in distal tubule AND VIT D3 activated to get more Ca and P absorption at the gut (also increased P transport)
Issue with increased P uptake:
fixing hypocalcemia, you are now hyperphosphatemic
Why does the increase in P occur?
Vitamin D levels
What inhibits the Na/P transporter in the proximal tubule:
parathyroid hormone, increasing its excretion (loss of na and Water, now that must be corrected)
Calcitonin functions:
inhibition of reuptake of Ca and P to lower blood Ca and P levels
Bone is stimulated by:
parathyroid hormone, vitamin d and calcitonin
When you want to leach Ca and P out of the bone:
stimulate osteocytes that release Ca and P in the canaliculi out of the bone, mobilize into blood pool, causing osteocytic osteo breakdown of bone without degrading the structure itself (parathyroid hormone and vitamin d are non-destructive), leave the matrix intact
Function of ?
restore pool and mobilize Ca and P out of bone and into he blood
Turns inactive to active Vitamin D form:
parathyroid hormone
Where is the phosphate sensor?
proximal tubule of kidney
low phosphate levels:
activate hydrolase to convert inactive vitamin d to active
hypophosphatemia is caused by:
malnutrition, alcoholism, respiratory alkylosis
vitamin d effect on gut:
increases Ca and P in gut
First line of defense is here to normalize Ca and P levels
gut, then bone
intracellularly transport across gut or take p from bone:
p levels are restored, now we are hypercalcemic, sensed by chief cells,
inhibt parathyroid hormone:
block resorption (decreases activity of Calcium pump in distal tubule and a little effect on the resporption of P in the poximal tubule)
glucocorticoids effect on bone:
long term bone growth retardation
cortisol or increases stress, effect on Ca and P levels:
block the transport of Ca and P across gut because the actions of —
another function of glucocorticoids:
effect differentiation of osteoblasts (decrease activity, can’t lie down fresh osteoid matrix)
Which bones will be targeted first for bone breakdown?
compact bone and those with a larger tissues content
High calcium levels:
inhibition of parathyroid hormone levels
dehydrocholesterol + light:
cholecalciferol (non-active vitamin d3, broken steroid nucleus, lipophilic, enters epithelial cells)
free calcium is the killer, active vitamin d damage is prevented by;
calbindin
Where is cholecalciferol activated?
liver 25 hypoxie vitamin d (low biological activity)
Which form of Vitamin D is floating around in blood?
25 hydroxycholecalciferol vitamin d
hormonal regulation point for active vitamin d:
1-hyroxylase that is sensitive to parathyroid hormone or low phosphate levels, activates inactive to active vitamin d3
Low calcium is sensed here:
parathyroid gland
