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Direct stimulation of bone resorption by thyroid hormones
The Journal of Clinical Investigation
|September 1, 1976
Summary
Thyroid hormones, thyroxine (T4) and triiodothyronine (T3), directly stimulate bone resorption in cultured rat bones. This finding helps explain metabolic disturbances associated with hyperthyroidism.
Area of Science:
- Endocrinology
- Bone Biology
- Calcium Metabolism
Background:
- Thyrotoxicosis is linked to hypercalcemia, osteoporosis, and elevated bone turnover.
- Direct effects of thyroid hormones on bone metabolism in organ culture were previously unreported.
Purpose of the Study:
- To investigate the direct impact of thyroid hormones on bone metabolism using organ culture.
- To determine if thyroxine (T4) and triiodothyronine (T3) directly influence bone resorption.
Main Methods:
- Cultured fetal rat long bones were treated with varying concentrations of T4 and T3.
- Bone resorption was quantified by measuring the release of incorporated 45Ca.
- Matrix resorption was assessed via dry weight, hydroxyproline concentration, and histology.
Main Results:
- Prolonged T4 and T3 treatment significantly increased 45Ca release, indicating enhanced bone resorption.
- Cortisol and calcitonin inhibited the thyroid hormone-induced bone resorption.
- Histological examination revealed increased osteoclast activity and matrix resorption.
Conclusions:
- Thyroxine (T4) and triiodothyronine (T3) directly stimulate bone resorption in vitro.
- This direct effect on bone resorption may elucidate calcium metabolism disturbances observed in hyperthyroidism.
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