Calcium Flashcards
__% of the body’s calcium is in bone
99%
The remaining calcium in the body that is NOT in bone (1%) is in the blood. Out of that 1%, about __% is ionized (free), about __% is bound to plasma proteins (albumin), and the remaining __% is bound to anions (phosphate, bicarbonate)
50%, 40%, 10%
___ is the most abundant mineral in the body
Calcium
Because calcium is relatively insoluble it is poorly absorbed from the intestinal tract unless you have Vitamin __
D
__/6’s of calcium is excreted via the feces while the remaining __/6 is through the urine
5/6’s, 1/6th
What are the two hormones involved in INCREASING plasma calcium?
- Parathyroid hormone (PTH)
2. 1,25 dihydroxycholecalciferol (1,25 DHCC)
What is the plasma calcium LOWERING hormone?
Calcitonin
Removal of half (2) of the parathyroid glands causes no abnormality, but removing 3/4ths causes transient ______
Hypoparathyroidism
Name the hormone:
- Releases calcium from bone
- Lowers the serum phosphorus levels
- Reduces the renal clearance of calcium
- Promotes the production of 1-25 DHCC in the kidney
Parathyroid hormone (PTH)
A component of 1-25 DHCC normally present in the diet
Cholecalciferol (D3)
D3 (cholecalciferol) has to undergo hydroxylation ___ before reaching full physiological activity
Twice
The first step of D3 hydroxylation (25-hydroxylation) takes place in the ____, while the second step (1-hydroxylation) takes place in the ____
Liver, kidney
Name the hormone:
- Important in the absorption of calcium from the intestine
- Also in deposition and resorption of calcium salts in bone
- May also have direct PTH-like effects on the renal tubule
1-25 DHCC
Another name for 1-25 DHCC?
Calcitriol
This hormone increases the activity of the activating enzyme AMP in the proximal tubules of the kidney, which increases conversion of calcidiol (25HCC) to calcitriol (1,25 DHCC)
PTH
___ causes increased renal reabsorption of calcium, increased GI tract absorption of calcium, and the drawing out of some calcium from bone
Calcitriol (1,25 DHCC)
___ inhibits renal tubule phosphate reabsorption, which results in loss of phosphorus into the urine
Calcitriol (1,25 DHCC)
When the serum calcium level is elevated on at least ___ separate determinations the patient is said to have hypercalcemia
3
____ calcium is the physiologically active form of calcium
Ionized (free)
The most common cause of hypercalcemia is _____
Hyperparathyroidism
The second most common cause of hypercalcemia
Malignancy
The two ways that a malignancy can cause hypercalcemia?
- Metastasis to bone causes bone destruction, increased serum calcium
- The cancer can produce PTH-like substance (ectopic PTH) that increases calcium levels
___ infections, such as sarcoidosis or TB are associated w/hypercalcemia
Granulomatous
___ occurs in patients w/hypoalbuminemia. MCC is malnutrition (especially alcoholics)
Hypocalcemia
Serum calcium is normally kept within narrow limits. What are they?
8.5-10.5 mg/dL
The correction of serum calcium for depressed albumin: Adjusted Calcium = ______
Serum calcium - serum albumin +4.0
If H+ falls (increased pH, alkalosis), calcium binds more to albumin and ionized calcium levels ____. The opposite is true if H+ rises (decreased pH, acidosis).
Fall
pH is inversely related to calcium (meaning if pH rises the (ionized) calcium falls)
True
Possible critical values for serum calcium:
<6.6 mg/dL (may lead to tetany)
>12.9 mg/dL (may lead to coma)
___mg of calcium is bound to 1.0g of albumin
0.8
If serum albumin is low, to correct, add 0.8mg/dL for every 1.0g/dL that serum albumin falls below ___g/dL
4.0
Multiple myeloma would cause ____albuminemia and in turn ____calcemia
Hyper, hyper
Dehydration causes ___ serum calcium levels
Increased
Venous stasis during blood collection by prolonged application of tourniquet would cause ___ serum calcium levels
Increased
If a patient has hypercalcemia, measure ___ next and ask about Vitamin D intake
PTH
Secondary hyperparathyroidism (renal rickets, renal osteomalacia) actually causes _____ before the normal hyperparathyroidism effects take place
Hypocalcemia
It seems in general that osteomalacia causes ___calcemia
Hyper
The most common malignant tumor causing hypercalcemia?
Breast
The most common cause of hypercalcemia in hospitalized patients
Malignant tumors (breast, lung, kidney)
The only common primary bone tumor to produce hypercalcemia
Multiple myeloma
__% of patients w/Hodgkin or non-Hodgkin Lymphoma would cause hypercalcemia due to ectopic production of 1,25 dihydroxy-vitamin D3
2%
By far, what are the three most common causes of hypercalcemia?
- Primary hyperparathyroidism
- Malignant tumors
- Drugs (i.e. Vitamin D/A intoxication, Diuretics, estrogens, thyroid hormone, etc.)
List the 3 possibilities that cause primary hyperparathyroidism:
- Adenoma
- Carcinoma
- Hyperplasia
Chronic renal failure is considered ____ hyperparathyroidism
Tertiary
Secondary hyperparathyroidism is caused by ___ deficiency
Vitamin D
Most common cause of borderline or slightly elevated hypercalcemia?
Artifact (lab error, excess venous stasis, serum protein elevation)
What are the two mnemonics for remembering hypercalcemia?
- CHIMPS
2. VITAMINS TRAP
CHIMPS stands for?
Cancer Hyperthyroid Iatrogenic Multiple Myeloma Primary hyperparathyroidism Sarcoidosis (Granulomatous disease)