PTH is secreted by the parathyroid glands, increases the number and activity of osteoclasts so their functions are Antagonistic. CT and PTH are also in charge of the hormonal control of blood calcium. This is the calcium negative feedback loop. When calcium in blood decrease the thyroid gland will secreted more PTH , PTH will simulate osteocalsts degrade bone matrix and release calcium into blood This process in called bone resorption. When calcium in blood increase more CT and less PTH will be secreted and it will simulate calcium deposited in bone, then bring blood calcium back to normal.Sex hormones can Promote the growth of new bone but it also Bring about the degeneration of cartilage cells. so it is a Double-edged sword. Then we will talk about aging.Aging for skeletal syetem happens when Osteoblast activity declines, while osteoclast activity remains level. This causes the loss of calcium from bones, which have tight relation with one disease ,we will talk about it later. Now let’s see another question.For female, this loss begins after age 40 but for male , this loss typically does not begin until after60. So Why? The answer is MENOPAUSE(更年期) Remember, estrogen(sexhormone for female) stimulates osteoblast activity and synthesis of bone matrix. As you can see in the picture decrease in estrogen cause bone loss.While man continue to produce androgens (sex hormone for male) into late life and thus are not as affected. Another effect for aging is the decrease in the rate of protein formation. Less organic matrix more inorganic matrix Bones become brittle and easy to fracture. Here is the disease I mentioned before, When the loss of bone mass compromises normal function a person is diagnosed with osteoporosis. As you can see the bones become brittle and easy to fracture. And here is the risk factors for osteoporosis. And the points in red are what we can change so the prevention of osteoporosis are No smoking Take in more calcium Don’t sit all the day Be careful when taking drugs. At last hope you have strong bones! Thank you!。
