Flashcards in Nephro - Calcium - Online MedEd Deck (38):
Pathophysiology of calcium...
Parathyroid glands behind the thyroid
-Have cells that have packaged parathyroid hormones in vesicles
-There is a calcium sensing receptor, which is inhibitory. If Calcium rises, then calcium turns OFF release of PTH
-Calcium level, PTH released
-PTH is primary way body manages Calcium
What are the effects of PTH?
3 different organ systems
1) Bone - cause resorption of bone (osteoclasts clear bone... release minerals) - elevation of Ca and Phos
2) Kidney - turns on 1,25-vitamin D --> turns on absorption of calcium in gut - resorption of calcium and excretion of phosphorus. There is also creation of vitamin D which goes to the gut
3) Gut (indirect) - activated by 1,25 vitamin D --> absorption of both calcium and phosphorus
** If kidney is working, kidney always wins = so too much PTH --> calcium elevate, and phosphorus falls!
What is another system that can effect PTH?
1,25 vitamin D secreted from granulomas such as TB/sarcoid --> which can activate the same 3 organ systems
Most calcium is bound to what?
About 1% is free ionized calcium
Normal albumin is 4
Normal calcium is 10
-If albumin changes by 1, then calcium changes by 0.8 in same direction. So Albumin of 3, means calcium of 9.2
-Albumin is typically low
Most calcium disorders can be determined by checking 3 things
Sometimes check vitamin D level
Hypocalcemia - presentation
Trousseau sign - inflate BP cuff, induce latent tetany
Chvostek's sign - tap facial nerve, side of face will contract
What should you do if you see hypocalcemia on labs?
-Corrects with albumin
-Not a deficiency of calcium
-Just a product of albumin
If hypocalcemia and albumin does not correct... need to check ionized calcium (this is in the absence of signs of hypocalcemia)
If ionized calcium is low
How to give calcium? IV calcium gluconate/carbonate
Management of hypocalcemia
Give IV calcium (gluconate/carbonate)
Hypercalcemia - presentation
Don't have symptoms of hypercalcemia... what to do?
If recheck shows elevated calcium, then treat. If normal, then stop
Treatment of hypercalcemia
If asymptomatic --> diagnose
If symptomatic --> needs treatment first
Treatment used to be fluid and lasix. Lasix blocks the paracellular calcium absorption in ascending loop of henle --> calciuria
*Loop diuretic/lasix actually has been found to drive the fluid out/drain and cause calcium to be concentrated
***So main treatment of hypercalcemia = VOLUME (lots of fluids). IV fluids!!
Treatment of hypercalcemia - 3 phases
1) Intermediate phase - calcitonin (IV - calcium "tone down")
2) Long term phase - bisphosphonates (standard)**
3) Indeterminate phase - loop diuretics (only give when volume up)
*So most importantly is fluids and bisphosphonates
So persistent hypercalcemia but no symptoms... differential
Hyperparathyroidism - 3 categories
1) Primary - autonomous secretion - from a single gland, generally noncancerous
2) Secondary - product of early renal failure, this is an appropriate response to relative hypocalcemia
3) Tertiary - also autonomous (multiple adenomas)
Hyperparathyroidism - presentation
Pathologic fractures - decreased bone density
Brown tumours (not malignancy) that eat away bone
Dx of hyperparathyroidism
Elevated PTH, Elevated Ca, Low Phos
Inappropriate elevation of PTH --> kidney wins, so calcium goes up and phos goes down --> calcium does not turn off PTH
*Do not need vitamin D
Due to autonomous production of PTH from gland
How to differentiate primary, secondary, and tertiary?
Get sestamibi scan
There are 4 parathyroid glands. If primary --> will get 1 gland with adenoma making PTH regardless of Ca. Other parathyroid glands are atrophied/suppressed by elevated Ca
Tertiary hyperparathyroidism --> multiple areas/adenomas that secrete PTH
Chronic low Ca due to inability to make vita D --> up regulate PTH appropriate --> constant stimulation of glands --> multiple areas that secrete PTH
Treatment of hyperparathyroidism
Is surgical resection
And hypoparathyroidism because the other glands have atrophied
Cinacalcet (calcium mimetic agent) is used in CKD to prevent tertiary hyperparathyroidism --> to prevent the amount of PTH made
Hypercalcemia associated with malignancy - pathophys
Cancer can either...
1) Mets - invades bone - causes a release of calcium and phosphorus --> this inhibits PTH release --> so PTH is low (kidney can't win... no PTH to stimulate the kidney... so Phos will be high as well as calcium)
2) Paraneoplastic syndrome - secrete PTH-related peptide (PTHrP) this is in squamous cell carcinoma of the lungs
Tumour invasion/cancer leads to what values on labs?
Elevated calcium and phos
PTHrP with SCC lungs - what values on labs?
This is PTH
So kidney is working and kidney wins
Elevated Calcium, Low Phos
Natural parathyroid glands are working --> so PTH is LOW
-Now measure PTHrP on labs!
Difference between mets and PTHrP on labs
Hypervitaminosis D - how to get this?
Over-ingested vitamin D (uncommon)
Granulomatous disease - excess vitamin completed vitamin D (1,25) is made
With lots of vitamin D, will absorb calcium and phos from gut. Because glands are working, Ca will inhibit PTH from glands.
Labs on hypervitaminosis D/granulomatous disease?
Elevated Ca and Phos. Low PTH
This looks a lot like Mets!
The difference - history of sarcoid, TB
Measure a 1,25 vitamin D to determine granuloma or mets
Hypercalcemia of immobilization
Calcium is elevated because there is immobility (i.e. maybe orthopedics/trauma)
-So PTH is low
-So kidney doesn't win
-Phos is elevated
Familial hypercalcemic hypocalciuria
Asymptomatic elevation of Calcium (11-12 range)
Check urine calcium... will be low
Usually asymptomatic, there is family history
Hypoparathyorid - differential
1) Iatrogenic - thyroid surgery, accidentally take out parathyroids as well; or parathyroid resection surgery
Post-op day 1 of thyroid surgery - will see what symptoms?
Perioral tingling, tetany
Dx: Low PTH, low Ca, phosphorus is irrelevant
Treatment is IV calcium!
Pseudohyperparathyroidism - what is this?
End organ resistance to PTH
PTH insensitivity. As though low PTH. But PTH levels will be elevated!
Dx of pseudohyperparathyroidism
PTH is HIGH (PTH insensitivity)
But Calcium is low and phosphorus is low
Vitamin D deficiency - where does vitamin D come from
Vitamin D comes from sunshine and dairy products
Patients with vitamin D deficiency - will present with
Dexa scan -2.0
No dairy products/stays inside all day
For vitamin D deficiency - what should we get?
A 25-vitamin D level
Not a 1,25 vitamin D level
Treatment of vitamin D deficiency
High dose PO vitamin D - if hypocalcemia is not bad, just give vitamin D
IV calcium - given for hypocalcemia
Bisphosphonates - for severe osteopenia
Chronic kidney disease
When Cr isn't bad, early CKD --> impairment of vitamin D formation --> secondary hyperparathyroidism (vitamin D can't absorb calcium)
Late stage CKD --> hypophosphatemia