Flashcards in PTH, Minerals, Vit D Deck (54):
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 PTH of 165 is?
A PO4 of 2.8 is?
What is the MCC of hypercalcemia in an outpatient setting?
What are the top three causes of primary elevation of PTH?
– 85% benign parathyroid neoplasm or adenoma – 10% parathyroid hyperplasia (3% MEN)
– 2% parathyroid carcinoma
**Usually doesn't cause serum Ca >12 mg
What percentage of patient's with primary hyperparathyroidism have bones, stones, groans and moans?
<20%! Most people are asymptomatic
Usually in F in pts >45 yrs, otherwise similar sex diffs
In addition to PTH and PO4 what other lab tests hsould you order?
urine Ca (24 hr preferred)
How do you evaluate hypercalcemia?
Total Ca >10.5 or ionized Ca >5.6
causative diseases vs meds
measure intact PTH level
24 hr urine Ca level
If 24 hr urine Ca is low....
familial hypocalciuric hypercalcemia
If 24 hr urine Ca is normal/high...
Describe Ca equilibria in blood
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
What happens to free Ca in alkalemia?
HIGHER pH --> free Ca decreases, increase in Pr-bound Ca
What happens to free Ca in acidemia?
LOWER pH --> free Ca increases, Pr-bound Ca decreases
For each .1 change in pH, free Ca changes by ....
Does total Ca change?
What is the major clinical utility of ionized Ca?
1. Ensure maintenance of hemodyanmic fxn
2. monitor pts in critical care
- higher mortality in septi pts with hypocalcemia
- pts w/ pancreatitis/renal disease
3. diagnose/treat hypercalcemic/hypocalcemic conditions
What reflects TRUE Ca status, is unaffected by protein concentration and requies stringent collection/handling because its pH sensitive?
Free (ionized Ca)
What reflects (free + protein-bound + anion bound), depends on protein concentration and is not affected by pH?
What formula is often use to correct Ca to account for protein?
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
How do you correct iCa for pH changes?
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
When should iCa be tested?
total Ca is <8 or >10.2
How can parathyroidectomies be guided by serum PTH concentrations?
• 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
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?
What is the MCC of hypercalcemia in the outpatient setting when Ca < 12
What causes hypercalcemia by increasing synthesis of 1,25-(OH)2 vitamin D from macrophages within the granuloma?
macrophages in the granuloma increase synthesis of vit D
What vitamin intoxication can increase Ca to 12-14 mg/dL?
vit A (50,000 to 100,000 IU)
What lab tests would you order to confirm the diagnosis of an occult malignancy causing hypercalcemia?
iPTH was 20... Suppressed
Do a sxs guided malignancy work up
What are labs to test for solid tumors?
increased PTHrP: adeno and sq cancer (lung tumor)
Increased alk phosphatase: bone lysis (breast tumor)
What are labs for hematologic malignancies?
+ myeloma screen: MM
increased calcitriol: lymphoma, granulomatous disease
What is PTHrP?
it is DISTINCT from PTH but has some N terminal homoogy so can interact with the PTH receptor and mimic PTH activity
What is the normal range for PTHrP?
(collect and process on ice with protease inhibitors!)
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
WHAT COULD BE THE CAUSE OF THIS PT'S HYPOMAGNESEMIA?
– Medication (diuretics, cisplatin, aminoglycosides, cyclosporine)
– Infection (pyelonephritis, glomerulonephritis)
– Osmotic diuresis
– Diarrhea, vomiting
– Laxative abuse
– Lack of intake or absorption of dietary Mg
• Leads to secondary hypoparathyroidism
What is PPIH?
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
12 mo M presents for pediatric WCC
- breastfed since birth
- meeting mile stones
- mild vaglus varus both legs
• 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?
Vit D def
If you suspect vit D def in a child what other tests would you order?
What is required to convert 25 OH vit D to 1,25 OH vit D?
D3 vs D2: syntehsized in the body
D3 (D2 plant)
D3 vs D2: synthetically derived supplement
D2 (D3 natural)
Leads to a sigfniciant increase in total 25OH vit D in body
D3 (D2 only moderate)
What form of vit D is recommended by experts for optimal bone and immune support?
What lab is the best indication of a patient's true vitamin D status?
25-OH (t1/2 2-3 weeks)
How does vit D prevent hypocalcemia?
it inhibits PTH
What biochemical changes are assocaited with vit D deficiency?
Decrease in 25OHD
INCREASE in PTH
Eventual decrase in Ca/Phos
What is Rickets?
• 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
What are signs of Rickets?
• Skeletal deformities (delayed fontanelle closure, bowed legs, breastbone projection)
• Unable to stand or walk
• Slow growth
• Bone pain and tenderness
• Dental deformities
Where is Rickets becoming more common now?
(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
What sort of supplementation is required for every age?
– Birth – 1y: 400 IU
– 1-70y: 600 IU
– 71+ y: 800 IU
– Breastfed infants need supplementation!
How much vit D shoiuld you get during pregnancy?
• 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
How much vit D supplementation is recommended for neonates?
Breast milk is DEFICIENT in vit D
How much vitamin D should lactating women receive?
What can be used for 25OH vit D screening?
What is the most accurate test used to test for vit D def and who should it be used for?
pts on vitamin D supplementation
Where is the greatest prevalence of vit D def?
What indicates a vit D def?
<20 (20-60 ref range)