PTH/Minerals/Vitamin D Flashcards
What electrolyte abnormalities do you see with primary hyperparathyroidism?
hypercalcemia hypophosphatemia maybe (only seen in 50%
What is the most common cause of primary hyperthyroidism?
benign parthyroid neoplasm or adenoma
What are the other two main causes of primary hyperparathyroidism?
parathyroid hyperplasia
parathyroid carcinoma
Patients with primary hyperparathyroidism are usually asymptomatic, but if they do have symptoms what would you expect?
bones, stones, groans, psychiatric overtones
After diagnosing primary hyperparathyroidism, would you order any other lab tests?
urine calcium (24 hr is better than random)
If you find that the 24 hr urine calcium is low, what is the diagnosis?
familial hypocalcuric hypercalcemia
What are the three different forms of calcium in blood?
protein-bound (40-45%)
free (ionized) (45-50%)
complexed (PO4, HCO3, Lactate), 5-10%
How does pH affect the free calcium levels?
Alkalemia DECREASES free calcium (more bound to albumin)
Acidemia INCREASES free Ca
so Ca binding is directly correlated to pH; lower pH = less binding = more free Ca
for each 0.1 change in pH, free Ca changes by 5%
What is the main purpose of free ionized calcium?
maintenance of hemodynamic function: cardiac contractility, vasoactive tone, etc.
Why do you need to correct the total calcium to account for protein?
Because higher protein levels will lead to more calcium bound and increase the total calcium even though that bound calcium isnt doing anything and we don’t care about it.
What is the equation for the corrected total calcium?
measured total Ca + 0.8*[4-Albumin]
What do we need to correct the free ionized calcium level for?
pH level
What is the iCa pH correction formula?
Measured iCa[1-0.53(7.4-measured pH)]
When do we test the ionized calcium?
Really only used as a reflex test if the total calcium is less than 8 or more than 10.2
What are the three circulating forms of PTH?
First, PTH starts as a peptide with an N and C terminal, which are variable cleaved.
So:
- Intact, bioactive OTH
- N-truncated PTH
- C-terminal fragments
Parathyroidectomies may be guided by serum PTH concentrations. A decrease in PTH of what in 10 minutes post-resection signals success in removing the abnormally secreting parathyroid tissue.
over 50%
What are some renal causes of hypomagnesemia?
meds (diuretics, cisplatin, aminoglycosides, cyclosporin)
infection (pyelo, glomerulo)
Osmotic diuresis
What are some GI causes of hypomagnesemia?
diarrhea, vomiting laxative abuse lack of intake/absorption malabsorption malnutrition alcoholism TPN
How does hypomagnesemia lead to secondary hypoparathyroidism?
…
How do you exclude renal loss of Mg?
check urine Mg
How long does someone need to be on PPIs before they develop hypomagnesemia?
median # of years before onset is 5.5
In an infant with elevated PTH and normal calcium, what lab should you check?
vitamin D level!
What vitamin D level should you test to get the most accurate idea of a patient’s true vit D status?
25-OH
Can your body still form vitamin D if you wear sunscreen?
Not nearly as much. Whole body SPF 8 reduces the capacity to produce Vit D3 by 95%
What biochemical changes do you see in late stage Vit D deficiency?
Low calcium
low phos
way low urinary Ca
increased PTH
What is the disease state with vit D def in kids?
Rickets
What are the signs of rickets?
skeletal deformities (delayed fontanelle closure, bowed legs, breastbone projection)
weakness unable to stand/walk slow growth bone pain/tenderness seizures (hypocalcemia) dental deformities
Vitamin D def is associated with what other deficiency?
iron
and interestingly, treatment with iron can increase vitamin D levels!
What group of patients definitely need Vit D supplementation without question?
breastfed infants
