Calcium and Parathyroids

Question 1

Why is calcium important?

Answer 1

-Nerve conduction
-Bone formation
-Muscle function
-Blood coagulation
-Cerebral and cardiac function
-Capillary permeability
-Cell growth and division
-Neurotransmitter action

Question 2

How much calcium does the body contain?

Answer 2

1-2 kg

-1,000 grams
-1,000,000 mg

Question 3

Where is calcium stored?

Answer 3

-98% in skeleton
-1% in cells
-0.1% in ECF
-0.03% in plasma

Question 4

What is the ionized form of calcium important for?

Answer 4

50% ionized (active form)
-functions on the heart, nervous system and bone formation

Question 5

What protein is calcium primarily bound to?

Answer 5

albumin (41%) - not diffusible across capillary membranes

Question 6

in what form is calcium diffusible?

Answer 6

Combined with anions (9%) - citrate, bicarbonate, and phosphate

diffusible across capillary membranes

Question 7

Approximately ____% exists in an _____ and _____ form

Answer 7

Approximately 50% exists in an ionized and diffusible form

Question 8

What is the normal ionized Ca2+ level?

Answer 8

4.7-5.2 mg/dL

Question 9

What is the normal serum calcium level?

Answer 9

8.5-10.5 mg/dL

Question 10

What percent of bone calcium is readily exchangeable?

Answer 10

0.5%- rest is slowly exchangeable

The bone acts as a reservoir for calcium and can store and release calcium as needed.

Question 11

Active _____ increases ____, _____, ____ ion concentration by promoting their absorption across the intestinal epithelium to the extracellular fluid

Answer 11

Active vitamin D increase plasma calcium, magnesium, and phosphate ion concentration by promoting their absorption across the intestinal epithelium to the extracellular fluid

Question 12

What are the effects of Hypocalcemia?

Answer 12

Nervous system excitement
- increased neuronal permeability to Na+= easy action potentials

35% total decrease leads to spontaneous discharge

-Tetany, seizures
-Longer QT
-Hyperactive deep tendon reflexes = laryngospasm

Question 13

What is Trousseau’s sign?

Answer 13

Most common in the hand-carpopedal spasm d/t hypocalcemia

-inflate BP cuff slightly above systolic for 3 mins = ischemia = flexion of wrist and thumb, extension of fingers

Question 14

What is Chvostek’s sign?

Answer 14

Tapping facial nerve leads to twitching

Question 15

What are the clinical manifestations of hypercalcemia?

Answer 15

Skeletal muscle weakness
-Nervous system depression
-Short QT, prolonged PR interval
-constipation
-anorexia

Question 16

What is the treatment for hypercalcemia?

Answer 16

-Maintain UOP
-Hydrate
-Administer mithramycin in severe cases (antibiotic that has anti-neoplastic properties)

Question 17

How much phosphorus does the body contain?

Answer 17

1kg

Question 18

Where is the phosphorus in the body?

Answer 18

-85% skeletal
-15% muscle/tissue
-1% ECF

-Circulates in plasma 12% protein bound

Question 19

What is the major control site of phosphorus?

Answer 19

Kidney
-urinary excretion balances GI intake
-PTH increases urinary excretion and calcitonin to a lesser extent

Question 20

What increases GI absorption of phosphorus?

Answer 20

1, 25-dihydroxycholecalciferol
Vitamin D3

Question 21

What kind of cells do the parathyroid glands contain?

Answer 21

Chief cells
Oxyphil cells

Question 22

What do the chief cells secrete?

Answer 22

parathyroid hormone (PTH)

Question 23

When will parathyroid glands become enlarged?

Answer 23

-Prolonged stimulation
-pregnancy
-lactation

Question 24

What increases PTH secretion?

Answer 24

low calcium levels
high phosphorus levels

Question 25

What inhibits PTH secretion?

Answer 25

-Chronically high calcium levels
-chronically low magnesium levels
- acutely high mag levels

Question 26

What does PTH secretion do?

Answer 26

-increases extracellular calcium
-decreases extracellular phosphate concentration

Question 27

Decreases in calcium concentration in the extracellular fluid _____ the secretion of PTH

Answer 27

increases

Question 28

Increases in calcium concentration in the extracellular fluid _____ the activity of the _____

Answer 28

increases in calcium concentration in the extracellular fluid decreases the activity of the gland

Question 29

Where is calcitonin produced?

Answer 29

Thyroid parafollicular cells or C cells

Question 30

When is calcitonin produced?

Answer 30

In response to elevated serum ionized calcium.

Question 31

What effect does calcitonin produce?

Answer 31

Opposite of PTH- lowers serum ionized calcium concentration.

Inhibits osteoclasts
enables osteoblasts

Question 32

What is inactive vitamin D called?

Answer 32

Cholecalciferol

Question 33

What is the active product of Vitamin D?

Answer 33

1, 25-dihydroxycholecalciferol

Question 34

What helps with calcium reabsorption from the nephron of the kidney?

Answer 34

-PTH
-Vitamin D/cholecalciferol
-Calcitonin

Question 35

What are the actions of PTH?

Answer 35

-Increases bone resorption to mobilize calcium and phosphate

-Increases reabsorption of calcium in the kidney’s distal tubules

-decreases reabsorption of phosphate in the renal tubules

-Increases the production of 1,25-dihydroxycholecalciferol

-Major stimulus is low serum calcium levels

Question 36

Increased in PTH results in:

Answer 36

serum: increased calcium, decreased phosphate

urine: decreased calcium, increased phosphate

Increases the excretion of phosphate, potassium, and sodium by increasing the reabsorption of calcium, magnesium and hydrogen

DISTAL TUBULES AND COLLECTING DUCTS

Question 37

Where does PTH have direct effects?

Answer 37

Bone and kidney