Hormones and Bones

Question 1

how does most Ca travel in the blood?

Answer 1

bound to albumin

Question 2

calcium oxalate

Answer 2

kidney stones

Question 3

calcium phosphate

Answer 3

ectopic calcification in soft tissues

Question 4

hypocalcemia symptoms

Answer 4

CATS GO NUMB

convulsions
arrythmias (long QT)
tetany
spasms, stridor

numbness

Question 5

hypercalcemia symptoms

Answer 5

Stones (kidney stones)
Bones (bone pain)
Groans (abdominal pain, nausea)
Thrones (constipation, polyuria)
psychiatric overtones)

more common

treated w/ hydration and IV bisphosphate

Question 6

is vitamin D3 active or inactive?

Answer 6

inactive`

Question 7

how does the body sense calcium

Answer 7

Gq linked receptor (phospholipase C/IP3)- causes Ca release from ER

expressed in cheif cells of parathyroid (inhibits PTH)

principal cells and a-intercalated cells in kidney to promote Ca excretion

osteoblasts to promote bone remodeling

Question 8

parathyroid hormone synthesis

Answer 8

starts as prepro, cleaved to a pro in ER, cleaved in golgi to mature PTH for secretion

Question 9

parathyroid hormone receptor

Answer 9

Gs receptor- cyclic AMP

Question 10

PTH effects in bone

Answer 10

transient levels increase bone formation d/t effect on osteoblasts

chronic levels increase bone resorbtion via RANK system- increases free Ca

Question 11

PTH effects in kidney

Answer 11

increases Ca reabsorption, decreases PO4 reabsorption,

stimulates 25(OH)D3-hydroxylase

Question 12

causes of hypercalcemia?

Answer 12

90% are cancers in parathyroid gland

Question 13

vitamin D3 pathway

Answer 13

skin makes vitamin D3

liver converts it to 25(OH)D3

kidney converts to active 1,25(OH)D3

Question 14

vitamin D3 receptor

Answer 14

binds vit D in cytoplasm and translocates to nucleus and binds response elements with RXR

Question 15

vitamin D3 effects

Answer 15

90% of gut absorption of Ca

activates RANK system in bone osteoblasts/cytes

stimulates reabsorption of both Ca and PO4 in kidney

Question 16

RANK system

Answer 16

vitamin D3, PTH stimulate osteoblasts

osteoblasts present RANK ligands to osteoclasts

has 2 effects via NF-kB:
stimulates differentiation into osteoclasts

activates quiescent osteoclasts

Question 17

denosumab

Answer 17

competitive mAb for RANK ligand to prevent osteoporosis

Question 18

FGF23

Answer 18

secreted in response to vit D and PO4

causes PO4 secretion from kdiney

decrease PO4 absorption from gut

net: decrease serum PO4

Question 19

describe the bodies response to hypocalcemia

Answer 19

decreased activation of CaSR

causes:

increased PTH
increased Ca reabsorbtion via kidney
increased Ca/PO4 resorption in bone

PTH will then further increase Ca reabsorption (and PO4 secretion) and stimulate 1,25(OH)D3 hydroxylase

vit D will increase renal reabsorption via increase calbindin

PTH and vit D will activate RANK system at bone and cause resorbtion

vit D will also cause increased Ca absorption in gut

Question 20

describe bodies response to hypercalcemia

Answer 20

increased CaSR

causes:

decreased PTH
decreased renal Ca reabsorption
increased bone mass

decreased PTH causes decreased Ca renal absorption, and decreased Vit D3

decreased PTH will suppress RANK system

Question 21

osteoporosis

Answer 21

d/t increased reabsorption of bone

in postmenopausal women, d/t decreased estrogen

excess cortisol, thyroid hormone, hyperparathyroid or low Ca diet

treatment: exercise

Question 22

rickets/osteomalacia

Answer 22

rickets- prior to epiphyseal closure, osteomalacia is after

caused by Vit D deficiencies

• genetic
• anticonvulsants
• aluminum toxicity
• excess flouride

treated w/ vitamin D3 and phosphate

Question 23

what cells in the parathyroid hormone release PTH

Answer 23

chief cells