20. Calcium regulation and pharmacology

Question 1

Function of calcium in the heart

Answer 1

Phase 2 of cardiac action potential

Calcium-induced-calcium release

Question 2

Normal Ca levels in plasma

Answer 2

8.5-10.4 (9mg)

45% ionized Ca exters physiologic effects

Question 3

WHat percent of Ca is stored in the bone?

Answer 3

99%

Question 4

Myocardial cell contraction

Answer 4

stimulate cardiac muscle –> sodium entry, potassium exit, Ca entry (during phase 2) –> SR release of Ca –> troponin C inding, actin + myosin interact

SR reabsorbs Ca; rebinds to internal membrane –> heart relaxes

Question 5

Functions of Ca

Answer 5

Nerve funciton (NT release)
Cardiac Potential
Membrane integrity (Ca ions allow for membranes to remain stable and bound; give IV Ca to patients with membrane destruction)
Blood coagulation
Second messenger/hormone signal amplification

Question 6

Is all of the Ca you intake in diet absorbed?

Answer 6

No

Question 7

Cardiovascular meds effect on Ca levels

Answer 7

they alter Ca levels

Question 8

Vit D effect on Ca absorption for GI

Answer 8

inc. absorption in prox duodenum

Question 9

PTH effect on Ca in kidney

Answer 9

Reabsorb Ca from kidney

Question 10

Drugs that depress intestinal Ca transport

Answer 10

Glucocorticoids, phenytoin

Phytate, oxylate

Question 11

Why might patients with thyroidectomy have seizures?

Answer 11

calcemic dysregulation (hypocalcemic)

Question 12

Furosimide and Ca

Answer 12

Furosemide causes hypocalcemia

Inhibit NKCC2 pump –> hypokalemia, hypocalcemia

Question 13

Thiazide effect on Ca

Answer 13

Inc reabsorption of Ca (used to treat calcium stones)

Question 14

High dose corticosteroids effect on bone

Answer 14

dec osteoblast activity –> dec bone formation

Question 15

Tx for hypercalcemia

Answer 15

Calcitonin

Fluids (increase GFR for increased Ca loss)

Question 16

Hypocalcemia effect on heart

Answer 16

Decrease in ionotropism

Question 17

Signs and symptoms of hypocalcemia

Answer 17

Tetany
Paresthesias (numbness)
Increased neuromuscular excitability (hyperreflexia)

Question 18

EKG changes with hyper and hypocalcemia

Answer 18

Hypercalcemia = QT interval shortening 
Hypocalcemia = prolonged QRS

Question 19

What effect does a decrease in phosphate have on calcium?

Answer 19

stimulates calcium mobilization

Question 20

PTH effect on phosphate, ca

Answer 20

increases urinary excretion of phosphate, bone resorption to increases serum ca levels, intestinal Ca absorption (indirect), limit ca excretion

stimulate conversion of vit D to calcitriol in kidney

Question 21

What is Rickets? Osteomalacia?

Answer 21

Rickets: Def of vit D in children
Irregular bone formation

Osteomalacia: Def of vit D in adults; defective bone mineralization

Question 22

Which hormones can stimulate CT release? Half-life?

Answer 22

Glucagon, gastrin, serotonin

10min (short)

Question 23

Bisphosphonates

Answer 23

Etidronate, pamidronate

Inhibit bone resorption, unknown how but thought to be because they are incorporated into bone matrix and inhibit osteoclast from resorbing the bone

Question 24

Alendornate MOA

Answer 24

inhibits osteoclast-mediated bone resportion via preferential localization to the site of bone resorption

Question 25

Raloxifene

Answer 25

Selective estrogen receptor modulator
Reduces bone turnover by decreasing osteoclast activity

SE: flu-like symptoms, hot flashes, arthralgia; worse SE in patients that are menopause symptoms already present

Question 26

Quickie reference list of drugs:
Alendronate
Calcitonin
Calcitriol
Dihydrotachysterol/ergocalciferol
tidronate
Pamidronate
Raloxifene

Answer 26

Alendronate = osteoporosis
Calcitonin = paget's disease, post menopausal osteoporosis, hypercalcemia of malignancy
Calcitriol = metabolic bone disease for renal failure
Dihydrotachysterol/ergocalciferol = Vit D replacement
Etidronate= Paget's disease, osteoporosis
Pamidronate = hypercalcemia of malignancy
Raloxifene = postmenopausal osteoporosis