Parathyroid

Question 1

Body Ca2+ levels are regulated mainly by three hormones;??

Answer 1

Body Ca2+ levels are regulated mainly by three hormones; parathyroid hormone (PTH), Vitamin D and calcitonin.

Question 2

Ca2+ in essential metabolic activities including

Answer 2

neuromuscular excitability,
excitation-contraction coupling in muscle,
stimulus-secretion coupling,
maintenance of cellular tight junctions,
blood clotting,
and structural and functional integrity of bone and teeth

Question 3

Parathyroid hormone related peptide (PTHrp), plays a role in

Answer 3

Pendochrondral bone growth,
resorbing aveolar bone to allow normal tooth development and eruption
maintaining elevated Ca2+ levels in fetal circulation during pregnancy and
mobilization of Ca2+ in mammary gland for secretion in milk during lactation.

Question 4

(CaSR)

Answer 4

Parathyroid gland chief cell release of PTH is regulated by a Ca-sensing receptor (CaSR)

Question 5

role of Active Vit. D3

Answer 5

Active Vit. D3 supresses PTH synthesis and stimulates CaSR synthesis.

Question 6

PTH and its effect on the bones

Answer 6

BONE
PTH stimulates bone osteoblasts to increase growth & metabolic activity
PTH stimulates bone resorption and releases calcium & phosphate into blood

Question 7

PTH and its effect on the kidney

Answer 7

PTH increases reabsorption of calcium & reduces reabsorption of phosphate

Stimulates synthesis of Vitamin D3

Inhibits resorption of Na+ and bicarbonate in the proximal tubule and stimulates a Na+-H+ exchanger

Question 8

PTH and its effect on the INTESTINE

Answer 8

INTESTINE

Increases calcium and phosphate reabsorption via vitamin D

Question 9

fast exchange vs slow exchange of calcium

Answer 9

fast: calcium moves from the labile pool in bone fluid to the plasma
slow: calcium moves from sstable pool in the mineralized bone to the plasma

Question 10

calcitonin is secreted by

Answer 10

Calcitonin is a peptide hormone secreted by the parafollicular or “C” cells of the thyroid gland

Question 11

calcitonin function

Answer 11

Calcitonin acts on bone osteoclasts to reduce bone resorption.
Net result of its action is a decline in plasma calcium & phosphate

Question 12

Calcitonin appears to have no physiological role in the regulation of plasma Ca2+ in humans.

T/F

Answer 12

T

Question 13

Increased PTH

CAUSES

Answer 13

Increased PTH
Resulting in mobilization of bone Ca2+ & PO4-, increased renal phosphate excretion & Ca retention and increased Vitamin D3 synthesis

Question 14

Primary hyperparathyroidism

Answer 14

hypercalcemia, 
hypophosphatemia, 
hypercalciuria 
and renal calculi (renal stones)
Usually has no clinical expression in bone

Question 15

Long-term secondary hyperparathyroidism

Answer 15

renal failure generated hyperphosphatemia and hypocalcemia

is associated with accelerated bone resorption

Question 16

HYPOPARATHYROIDISM

Answer 16

increased bone mass 
hypocalcemia and hyperphosphatemia  
increased neuromuscular excitability 
numbness and tingling sensations,
 tetanic muscle contractions and seizures