Posted by good from IP 24.195.202.163 on April 30, 2006 at 08:07:11:
In Reply to: mechanism of osteoprosis in hyperthyroidism? posted by Nadia on April 30, 2006 at 05:56:00:
Thyroid hormone increases the creation of new bone remodeling units with an enhancement of remodeling activity. Thyroid hormones directly stimulate production of osteocalcin and alkaline phosphatase. In patients with thyrotoxicosis, increased serum levels of osteocalcin and alkaline phosphatase may be seen. Despite the increase in osteoblast activity, there are also thyroid hormone–induced increases in bone resorption. The bone resorption is associated with increased levels of hydroxyproline and collagen cross-links in thyrotoxic patients. The overall increase in bone turnover in the presence of excessive levels of thyroid hormone is characterized by an increase in the number of osteoclasts, the number of resorption sites, and the ratio of resorptive to formative surfaces. In the thyrotoxic patient, the bone remodeling cycle is shortened because of a decrease in the length of the bone formation and, overall, there is failure to replace resorbed bone completely, leading to bone loss.
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