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LAMP > PTH, Minerals, Vit D > Flashcards

PTH, Minerals, Vit D Flashcards

1
Q

Pt has c/o mild fatigue and an elevated serum Ca of 11.5. What is the most likely cause of this patient’s hypercalcemia? Would you order any other lab tests?

A

Hyperparathyrdoidism?

PTH
PO4

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2
Q

A PTH of 165 is?

A

HIGH!

normal 15-75

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3
Q

A PO4 of 2.8 is?

A

low

normal 2.5-4.5

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4
Q

What is the MCC of hypercalcemia in an outpatient setting?

A

primary hyperparathyroidism

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5
Q

What are the top three causes of primary elevation of PTH?

A

– 85% benign parathyroid neoplasm or adenoma – 10% parathyroid hyperplasia (3% MEN)
– 2% parathyroid carcinoma

**Usually doesn’t cause serum Ca >12 mg

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6
Q

What percentage of patient’s with primary hyperparathyroidism have bones, stones, groans and moans?

A

<20%! Most people are asymptomatic

Usually in F in pts >45 yrs, otherwise similar sex diffs

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7
Q

In addition to PTH and PO4 what other lab tests hsould you order?

A

urine Ca (24 hr preferred)

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8
Q

How do you evaluate hypercalcemia?

A 
Total Ca >10.5 or ionized Ca >5.6 
>
causative diseases vs meds
>
measure intact PTH level
>
normal/high
>
24 hr urine Ca level
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9
Q

If 24 hr urine Ca is low….

A

familial hypocalciuric hypercalcemia

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10
Q

If 24 hr urine Ca is normal/high…

A

primary/tertiary hyperparathyroidism

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11
Q

Describe Ca equilibria in blood

A

High pH: Ca is bound to PROTEIN (albumin, globulins) 40-45%

Lower pH: Free (ionized)

Complexed: PO4, HCO3, Lactate (5-10%)

*All are pH dependent

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12
Q

What happens to free Ca in alkalemia?

A

HIGHER pH –> free Ca decreases, increase in Pr-bound Ca

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13
Q

What happens to free Ca in acidemia?

A

LOWER pH –> free Ca increases, Pr-bound Ca decreases

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14
Q

For each .1 change in pH, free Ca changes by ….

Does total Ca change?

A

5%

NO!

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15
Q

What is the major clinical utility of ionized Ca?

A
  1. Ensure maintenance of hemodyanmic fxn
  2. monitor pts in critical care
    - higher mortality in septi pts with hypocalcemia
    - neonates
    - pts w/ pancreatitis/renal disease
  3. diagnose/treat hypercalcemic/hypocalcemic conditions
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16
Q

What reflects TRUE Ca status, is unaffected by protein concentration and requies stringent collection/handling because its pH sensitive?

A

Free (ionized Ca)

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17
Q

What reflects (free + protein-bound + anion bound), depends on protein concentration and is not affected by pH?

A

Total Ca

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18
Q

What formula is often use to correct Ca to account for protein?

A 
Corrected Ca (mg/dL) = Measured Total Ca (mg/dL) + 0.8*[4-Albumin (g/dL)]
• Correction fails to accurately predict calcium status in individual patients
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19
Q

How do you correct iCa for pH changes?

A

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

  • Limited range of correction (pH 7.2-7.6)
  • Assumptions: patient has pH of 7.4, no variation in albumin, no additional iCa binding proteins or anions
  • Preferable to avoid pre-analytical issues entirely
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20
Q

When should iCa be tested?

A

total Ca is <8 or >10.2

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21
Q

How can parathyroidectomies be guided by serum PTH concentrations?

A

• Decrease in PTH of > 50% 10 minutes post-resection signals success in removing the abnormally secreting parathyroid tissue
• Rapid turnaround time is essential
– Shorter incubation
– Compromised sensitivity

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22
Q

47 year old female
• 5’4, 140 lbs
• BP: 110/90
• 2-week history of fatigue and midback pain (6 out of 10)
• Described pain as aching, worse in the morning and aggravated by movement
• Laboratory tests unremarkable except for serum total calcium of 16.7 mg/dL

+ Family hx for cancer

What is the most likely cause of this pts hypercalcemia?

A

occult malignancy

23
Q

What is the MCC of hypercalcemia in the outpatient setting when Ca < 12

A

hyperparathyroidism

24
Q

What causes hypercalcemia by increasing synthesis of 1,25-(OH)2 vitamin D from macrophages within the granuloma?

A

Sarcoidosis

macrophages in the granuloma increase synthesis of vit D

25
Q

What vitamin intoxication can increase Ca to 12-14 mg/dL?

A

vit A (50,000 to 100,000 IU)

26
Q

What lab tests would you order to confirm the diagnosis of an occult malignancy causing hypercalcemia?

A

iPTH was 20… Suppressed

Do a sxs guided malignancy work up

27
Q

What are labs to test for solid tumors?

A

increased PTHrP: adeno and sq cancer (lung tumor)

Increased alk phosphatase: bone lysis (breast tumor)

28
Q

What are labs for hematologic malignancies?

A

+ myeloma screen: MM

increased calcitriol: lymphoma, granulomatous disease

29
Q

What is PTHrP?

A

it is DISTINCT from PTH but has some N terminal homoogy so can interact with the PTH receptor and mimic PTH activity

30
Q

What is the normal range for PTHrP?

A

1-2 pmol/L

collect and process on ice with protease inhibitors!

31
Q

71 year old female referred to endocrinology clinic after several years of unresolved hypomagnesemia (NORMAL 1.7-2.5)
• Numerous hospital admissions to receive IV magnesium
• Previously presented with palpatations (x3) and once with diarrhea and vomiting
• Medical history included type 2 diabetes mellitus and hiatal hernia
• Medications: simvastatin, esomeprazole/Nexium, verapamil, pioglitazone, metformin
• Supplementation: calcium, magnesium, vitamin D
• Clinical examination unremarkable
• Normal ECG and echocardiogram

MG .52
CA 6.84

WHAT COULD BE THE CAUSE OF THIS PT’S HYPOMAGNESEMIA?

A 
• Renal
– Medication (diuretics, cisplatin, aminoglycosides, cyclosporine) 
– Infection (pyelonephritis, glomerulonephritis)
– Osmotic diuresis
• Gastrointestinal
– Diarrhea, vomiting
– Laxative abuse
– Lack of intake or absorption of dietary Mg 
– Malabsorption
– Malnutrition 
– Alcoholism 
– TPN
• Leads to secondary hypoparathyroidism
32
Q

What is PPIH?

A

PPI induced hypomagnesemia

  • Median # of years before onset: 5.5 years
  • Mechanism largely unknown
  • Clinical guidelines recommend obtaining serum Mg on new patients starting PPIs and regular monitoring of patients on long-term PPI therapy
  • Relatively rare complication
  • Patients at greater risk: GI disorders, diuretics
33
Q

12 mo M presents for pediatric WCC

  • breastfed since birth
  • meeting mile stones
  • mild vaglus varus both legs
  • CBC:normal
  • iPTH:334pg/mL
  • Phosphorus:2.5mg/dL • Magnesium: 2.3 mg/dL • Totalcalcium:9.7mg/dL

What is the most likely cause of this child’s elevated PTH?

A

Vit D def

34
Q

If you suspect vit D def in a child what other tests would you order?

A

25-hydroxyvitamin D

35
Q

What is required to convert 25 OH vit D to 1,25 OH vit D?

A

PTH!

36
Q

D3 vs D2: syntehsized in the body

A

D3 (D2 plant)

37
Q

D3 vs D2: synthetically derived supplement

A

D2 (D3 natural)

38
Q

Leads to a sigfniciant increase in total 25OH vit D in body

A

D3 (D2 only moderate)

39
Q

What form of vit D is recommended by experts for optimal bone and immune support?

A

D3

40
Q

What lab is the best indication of a patient’s true vitamin D status?

A

25-OH (t1/2 2-3 weeks)

41
Q

How does vit D prevent hypocalcemia?

A

it inhibits PTH

42
Q

What biochemical changes are assocaited with vit D deficiency?

A

Decrease in 25OHD
Decrease urCa
INCREASE in PTH

Eventual decrase in Ca/Phos

43
Q

What is Rickets?

A
  • Originated in late 1600’s
  • By 1900 > 80% children in industrialized cities in North America and Europe suffered from rickets
  • 1920’s: irradiation/fortification of milk became common practice; eventually saw eradication of rickets
  • C-sections increased; rate has remained the same since after WWII
44
Q

What are signs of Rickets?

A
  • Skeletal deformities (delayed fontanelle closure, bowed legs, breastbone projection)
  • Weakness
  • Unable to stand or walk
  • Slow growth
  • Bone pain and tenderness
  • Seizures
  • Dental deformities
45
Q

Where is Rickets becoming more common now?

A

(children): prevalent among immigrants from Asia, Africa, and Middle Eastern countries
• Vitamin D deficiency associated with Fe deficiency; treatment with Fe can increase 25(OH)D concentrations
• More likely to follow dress restrictions limiting sun exposure
• Darker pigmented skin converts UV rays to vitamin D less efficiently than lighter skin

46
Q

What sort of supplementation is required for every age?

A

– Birth – 1y: 400 IU
– 1-70y: 600 IU
– 71+ y: 800 IU
– Breastfed infants need supplementation!

47
Q

How much vit D shoiuld you get during pregnancy?

A
  • Current requirement: 600 IU
  • Supplementation with 800-1600 IU/day
  • Supplement with vitamin D3 or D2? D3 is what is quantitatively transferred in human milk
48
Q

How much vit D supplementation is recommended for neonates?

A

400 IU

Breast milk is DEFICIENT in vit D

49
Q

How much vitamin D should lactating women receive?

A

400 IU/day

50
Q

What can be used for 25OH vit D screening?

A

immunoassays

51
Q

What is the most accurate test used to test for vit D def and who should it be used for?

A

LC-MS/MS

CKD pts
pediatrics
pts on vitamin D supplementation

52
Q

Where is the greatest prevalence of vit D def?

A

Inpatients/hospitalized adults

53
Q

What indicates a vit D def?

A

<20 (20-60 ref range)

54
Q

What vit D levels are considered toxic?

A

> 150

LAMP (16 decks)

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