Parathyroid Disease Flashcards
calcium funciton
human skeleton
regulates degree of membrane excitability in nerve cells and muscle cells of GI and heart
nerve cells and hypercalcemia
cells are refectory to stimulation
hard to get the nerves excited
nerve cells and hypocalcemia
patients develop tetany or carpopedal spasm
nerves are very excitable
calcium levels in blood
9.5 mg/dL
half is bound to serum protein, half is ionized and active
calcium homeostasis maintained by
kidney, intestines, bones
hydroxylated vitamin D and parathyroid hormone
calcium palace in body
sensed by parathyroid and secretion of PTH increases
PTH immediate effects
stimulates kidney to hold on to calcium and bones to release calcium quickly bump up serum levels
PTH long term
PTH stimulates more absorption of calcium from gut by stimulating kidney to secrete vitamin D which acts at the gut receptor to increase calcium absorption
vitamin D
dietary intake or UV rays
biologically inert and must be hydrolyzed in body
vitamin D hydroxylation
skin/GI vitamin D
then goes to liver where it becomes 25-hydroxy-vitamin D (calcidiol)
finally goes to kidney where it goes to active 1,25-dihydroxy (calcitrol)
what do we use to measure vitamin D status
serum concentration of 25(OH)D
vitamin D toxicity
can cause non-specific s/s such as anorexia, weight loss, polyuria, and heart arrythmias
can raise blood levels calcium which leads to vascular and tissue calcification
calcium and the bones
bone balance is stimulated by exercise, anabolic, and anti-resorptive drugs
conditions that promote bone formation over bone resorption
effect of PTH (4)
- stops calcium excretion and promotes urinary phosphate excretion
- stimulates kidney to produce vitamin D
- activation of ostoeCLASTS
- stops activation of osteoBLASTS
normal calcium values
9-10.5 mg/dL
ionized levels - 4.5-5.6
severe calcium values
> 14 mg/dL
correct Ca
serum binding proteins (albumin) can cause falsely elevated levels
(Ca + 4) - albumin
what influences symptoms of high or low Ca
severity of derangement (farther from normal)
speed
hypercalcemia s/s
shortening of QT interval, HTN and bradycardia
hyperpolaziation of cell membrane
refractory to stimulation
skeletal muscle weakness
easy fatiguability and perceived muscle weakness
constipation, ileus, nausea, vomiting
increased GI acid production -PUD
volume depletion and renal failure
mental status change
workup of hypercalcemia
- confirm w/repeat lab, check albumin
2. check intact PTH
treatment of asymptomatic hypercalcemia
<12 mg/dL
hydration
avoidance of drugs that worsen (thiazides, lithium)
avoidance of factors that worsen it (bedrest, depletion)
treatment of severe hypercalcemia
> 14 mg/dL
aggressive IV normal saline to expand volume and IV bisphosphonate (Zometa)
hypocalcemia (nerve)
reduces ionic difference across cell membranes therefore making cells hyper excitable