PTH/Minerals/Vitamin D Flashcards Preview

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Flashcards in PTH/Minerals/Vitamin D Deck (29)
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1

What electrolyte abnormalities do you see with primary hyperparathyroidism?

hypercalcemia
hypophosphatemia maybe (only seen in 50%

2

What is the most common cause of primary hyperthyroidism?

benign parthyroid neoplasm or adenoma

3

What are the other two main causes of primary hyperparathyroidism?

parathyroid hyperplasia

parathyroid carcinoma

4

Patients with primary hyperparathyroidism are usually asymptomatic, but if they do have symptoms what would you expect?

bones, stones, groans, psychiatric overtones

5

After diagnosing primary hyperparathyroidism, would you order any other lab tests?

urine calcium (24 hr is better than random)

6

If you find that the 24 hr urine calcium is low, what is the diagnosis?

familial hypocalcuric hypercalcemia

7

What are the three different forms of calcium in blood?

protein-bound (40-45%)

free (ionized) (45-50%)

complexed (PO4, HCO3, Lactate), 5-10%

8

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%

9

What is the main purpose of free ionized calcium?

maintenance of hemodynamic function: cardiac contractility, vasoactive tone, etc.

10

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.

11

What is the equation for the corrected total calcium?

measured total Ca + 0.8*[4-Albumin]

12

What do we need to correct the free ionized calcium level for?

pH level

13

What is the iCa pH correction formula?

Measured iCa*[1-0.53*(7.4-measured pH)]

14

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

15

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:
1. Intact, bioactive OTH
2. N-truncated PTH
3. C-terminal fragments

16

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%

17

What are some renal causes of hypomagnesemia?

meds (diuretics, cisplatin, aminoglycosides, cyclosporin)

infection (pyelo, glomerulo)

Osmotic diuresis

18

What are some GI causes of hypomagnesemia?

diarrhea, vomiting
laxative abuse
lack of intake/absorption
malabsorption
malnutrition
alcoholism
TPN

19

How does hypomagnesemia lead to secondary hypoparathyroidism?

...

20

How do you exclude renal loss of Mg?

check urine Mg

21

How long does someone need to be on PPIs before they develop hypomagnesemia?

median # of years before onset is 5.5

22

In an infant with elevated PTH and normal calcium, what lab should you check?

vitamin D level!

23

What vitamin D level should you test to get the most accurate idea of a patient's true vit D status?

25-OH

24

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%

25

What biochemical changes do you see in late stage Vit D deficiency?

Low calcium
low phos
way low urinary Ca
increased PTH

26

What is the disease state with vit D def in kids?

Rickets

27

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

28

Vitamin D def is associated with what other deficiency?

iron

and interestingly, treatment with iron can increase vitamin D levels!

29

What group of patients definitely need Vit D supplementation without question?

breastfed infants