What is bone resorption?

[mariposas905]

I think bone resorption means breaking down of the bone and increasing osteoclast activity right?

So then how is this statement true? Estrogen does inhibit bone resorption; in fact, this is the reason why post-menopausal women experience significant declines in bone density.

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[canadianbacon1244]

You're exactly right. Bone resorption is the break down of calcium (i.e. bone) from increased osteoclast activity. Estrogen regulates osteoclast's apoptosis, so without estrogen, osteoclasts are able to run wild!

Fun fact: you hear of older women breaking their hip from a fall I'm sure. Well the bone becomes so weak that the initial break often happens when they put all of their weight on one leg to go up a step, and that alone causes a fracture, leading to them falling down and breaking a hip.

 

[mariposas905]

You're exactly right. Bone resorption is the break down of calcium (i.e. bone) from increased osteoclast activity. Estrogen regulates osteoclast's apoptosis, so without estrogen, osteoclasts are able to run wild!

Fun fact: you hear of older women breaking their hip from a fall I'm sure. Well the bone becomes so weak that the initial break often happens when they put all of their weight on one leg to go up a step, and that alone causes a fracture, leading to them falling down and breaking a hip.

Thanks! But the thing I don't understand is, if estrogen inhibits bone resorption (meaning it decreases bone breakdown), why do post-menopausal women still experience decreased bone density? Is it because estrogen levels are lower in older women?

 

[canadianbacon1244]

Thanks! But the thing I don't understand is, if estrogen inhibits bone resorption (meaning it decreases bone breakdown), why do post-menopausal women still experience decreased bone density? Is it because estrogen levels are lower in older women?

Ohhh I understand your question now. Yes, when women are post-menopausal, the amount of estrogen they have is minimal.
This is because of the female hormone pathway. They no longer release eggs, so you decrease FSH and LH. This decrease in FSH and LH will therefore decrease Estrogen and Progesterone production.
FSH and LH are no longer needed to support pregnancy.
More specifically, FSH promotes thickening of the endometrium to prepare for implantation, and LH promotes the formation of the corpus luteum (which in turn increases progesterone). I don't want to get too far into female reproduction and accidentally confuse you if I haven't done so already. Does this help?

 

[smukke]

Thanks! But the thing I don't understand is, if estrogen inhibits bone resorption (meaning it decreases bone breakdown), why do post-menopausal women still experience decreased bone density? Is it because estrogen levels are lower in older women?

Estrogen is low in post-menopause (think of estrogen replacement/HRT commercials you've seen for hot flashes)

Ohhh I understand your question now. Yes, when women are post-menopausal, the amount of estrogen they have is minimal.
This is because of the female hormone pathway. They no longer release eggs, so you decrease FSH and LH. This decrease in FSH and LH will therefore decrease Estrogen and Progesterone production.
FSH and LH are no longer needed to support pregnancy.
More specifically, FSH promotes thickening of the endometrium to prepare for implantation, and LH promotes the formation of the corpus luteum (which in turn increases progesterone). I don't want to get too far into female reproduction and accidentally confuse you if I haven't done so already. Does this help?

Close but you've got your hormone levels screwed up. Follicles depleted -> can't make estrogen/progesterone -> loss of negative feedback -> increased LH/FSH

 

[CommyO]

I think bone resorption means breaking down of the bone and increasing osteoclast activity right?

So then how is this statement true? Estrogen does inhibit bone resorption; in fact, this is the reason why post-menopausal women experience significant declines in bone density.

It's because bone resorption also promotes the rebuilding of newer and stronger bone. Since post-menopausal women have low levels of estrogen leading to low osteoclast activity, they retain their older less denser bones.