Parathyroid hormone

Question 1

What portion of Ca is regulated by PTH?

Answer 1

Ionized Ca

Question 2

Under acidic conditions what occurs to [Ca]?

Answer 2

less Ca is able to bind to albumin–causing a true increase in ionized Ca

Question 3

What is familial hypercalcemic hypcalcuria?

Answer 3

[Ca] is normally high without any symptoms

Question 4

What three main organ systems maintain Ca balance in the body?

Answer 4

IRS–intestine/renal/skeleton

Question 5

If kidneys can compensate for low Ca in the diet then what occurs and what is the consequence of this?

Answer 5

Increase in bone resorption causing loss of bone mass and density and can lead to osteoporosis

Question 6

Where is calcitonin produced and what role does it play?

Answer 6

Thyroid gland and is an inhibitor of bone resorption

Question 7

When is output of PTH high?

Answer 7

when [Ca] is low

Question 8

What effect does PTH have on the kidney?

Answer 8

Increase Ca re-absorption at distal tubule
Decrease re-absorption of PO4 at proximal tubule
Increase 1,25 diOHD3 synthesis

Question 9

What effect does PTH have on the bone cells?

Answer 9

Increase Osteoclastic resorption–increase Ca and PO4 in ECF and plasma
Osteocytic osteolysis–quick release of Ca

Question 10

High PO4 levels will cause what?

Answer 10

Increase PTH release–to stimulate exertion of PO4 into the urine

Question 11

Low Mg will cause what?

Answer 11

increased PTH release

Question 12

High Vit D will cause what?

Answer 12

Decreased PTH secretion–to stop conversion of 25-OHD3 to 1,25diOHD3 in the kidneys

Question 13

What effect does PTH have on the proximal tubule?

Answer 13

reduces PO4 re-absorption–reducing serum [PO4]

Question 14

What effect does PTH have on the distal tubule?

Answer 14

Increases Ca re-absorption

Question 15

Where does 60% of daily Ca re-absorption occur?

Answer 15

proximal tubule of kidney and is not controlled by PTH

Question 16

What effects does Vit D have on the intestine?

Answer 16

Increase Ca and PO4 absorption

Question 17

What effects does Vit D have on bone?

Answer 17

Stimulates osteoclastic resorption via receptors on osteoblasts

Increases Ca and PO4

Question 18

What effects does Vit D have on the parathyroid gland

Answer 18

Suppresses PTH secretion–neg feedback

Question 19

What effects does Vit D have on the distal tubule of the kidney?

Answer 19

Aids in Ca and PO4 transport

Question 20

What enzyme converts 25-OH-D3 to 1,25- diOH D3 in the kidney?

Answer 20

1-a-hydroxylase–enhanced by circulating PTH

Question 21

What is Rickets?

Answer 21

Chronic deficiency of Vit D and/or dietary deficiency of Ca or PO4 during early development–leads to disturbance in developing born formation –poor mineralization

Question 22

What is Humoral Hypercalcemia of Malignancy?

Answer 22

Cancer releasing PTH-related peptide which activated the same receptors as PTH–causing Serum Ca to increase from bone resorption and re-absorption in the kidney and PO4 loss

PTH is low due to High Ca inhibiting it

Question 23

What receptors do osteoblasts have and what do they tell osteoclasts to do?

Answer 23

PTH
Vit D
estrogen
paracrine and growth factors

Tell osteoclasts to mature and activate to resorb bone

Question 24

What is bone mineral?

Answer 24

Hydroxylapatite–Ca10(OH)2(PO4)6 with Mg and CO3

Question 25

What areas of skeleton rapidly lose or gain bone and what area is more stable?

Answer 25

Vertebrae and trabecular loose rapidly and tibia is more stable

Question 26

What from Osteoblasts cause activation of osteoclasts?

Answer 26

Cytokine from osteoblast lineage cells called RANK-L--binds to osteoclast precursors called RANK--receptor activator of NF-KB

Question 27

What inhibits RANK-L by binding to its sight?

Answer 27

OPG-osteoprotegerin--slowing down bone resorption