osteoporosis Flashcards
role of calcium (alot)
o Regulation of cell membrane permeability and functions, neuronal excitability and transmission of electrical impulses
o Contraction of cardiac, skeletal, and smooth muscle
o Conduction of electrical impulses in the heart
o Blood coagulation
o Platelet adhesion
o Hormone secretion
o Enzymatic activity
o Catecholamine release from the adrenal medulla
o Release of chemical mediators – histamines from mast cells
o Required for maintaining healthy bone and teeth
what is the function of the bone?
structural support and reservoir for calcium and phosphate
what is resorption
when serum levels are low in calcium, calcium will move from bone to blood stream
when will calcium move from bone to blood stream
if serum levels are low in ca
deposition
calcium from the intestines moves from diet onto bone
when does calcium move from intestines onto bone
when calcium on bone is not adequate
what is calcium deficiency caused by?
poor diet, hormonal altercations, medications
when someone is calcium deifcient, calcium moves from bone into the serum to compensate (resorption) what might this result in?
loss of bone mass, structural function and osteoporosis
what three hormones regulate calcium metabolism
PTH, Calcitonin, calcitriol
parathyroid hormone is secreted from what gland?
parathyroid gland
when are the parathyroid glands stimulated?
when calcium levels fall below normal
how does parathyroid hormone work to increase calcium resorption in kidneys
increases resorption in the renal tubules, reducing the amount in the urine, increasing amounts in serum
how does PTH increase the absorption of calcium in the small intestines
pth –> metabolism of vitamin d –> calcitriol
increases the absorption of calcium in the intestines
what is the active form of vitamin d
calcitriol
how does pth metabolize vitamin D into calcitriol
stimulates the metabolism of vitamin D into the active form
where is calcitonin form?
thyroid gland
when is calcitonin secreted
when calcium levels rise
when calcium levels rise what is secreted
calcitionin
how does calcitonin work in bone?
inhibits the activity of osteoclasts, stimulating the rate of bone deposition so calcium moves from serum to bone
what stimulates calcium to move from serum to bone
calcitonin
how does calcitonin work in the kidneys
works to inhibit resorption of calcium in the renal tubules –> more calcium excreted in the urine
what allows for more calcium to be excreted into the urine
calcitonin
what is called calcifdediol in the liver
calcitonin
when is vitamin d synthesized into its active form calcitriol
when serum levels are low
how does calcitriol work
works to enhance the intestinal absorption of calcium
if vitamin D deficiency results in low serum levels of calcium, what is going to happen
increased bone resorption and it can lead to osteoporosis
major risks of osteoporosis
- Major risk – female, gender, ancestry, a small lean frame, family history of osteoporosis
o Women with advanced age, early menopause, prolonged amenorrhea, decreased estrogen level
why would glucocorticoid administration be a risk factor for osteoporosis
because it inhibits bone deposition and increases bone resorption
Smoking calcium and vitamin d deficient diet, lack of regular exercise, increased caffeine and alcohol consumption, high salt diet are what in relation to osteoporosis
risk factors
treatment - how much calcium and vitamin d
1200 mg a day calcium
800-2000 iu a day of vitamin d
hormone replacement therapy is recommended for
women with moderate to severe symptoms of menopause
why does hormone replacement therapy work
ovarian hormones - estrogen and progesterone have a positive effect on bone mass density
how do selective estrogen receptor modulators work?
o Acts as an estrogen receptor agonist at beta-estrogen receptors in bone
Inhibits osteoclast activity reducing the rate of bone resorption
o Acts as an estrogen receptor antagonist at alpha estrogen receptors in breast and endometrial tissue
No increased risk of breast cancer
how do biphosphonates work?
increase bone mass density by inhibiting osteoclast activity, reducing bone resorption
rankl inhibitors
used to treat osteoporosis - work by binding to the rank receptor on osteoclasts promoting the removal of calcium from bone
what stimulates the upregulation of RANKL
estrogen deficiency, this will cause an increase in osteoclast function and significant bone loss during menopause
why do we have significant bone loss during menopause?
because estrogen deficiency upregulates the rankl increasing osteoclast function
who is the RANKL inhibitor a good choice for
women more susceptible to fractures
sclerostin inhibitors
inhibit sclerostin
what is sclerostin
small protien works to inhibit osteoblasts and bone formation
true or false; estrogen deficiency can increase sclerostin increasing bone loss
true
parathyroid is only recommended for what cases of osteoporosis
only very severe
