Effect of thyroid hormone on growth - Lessons from the syndrome of resistance to thyroid hormone

Thyroid hormone deprivation results in deleterious effects on bone growth. Delayed bone development is mediated by a direct effect of thyroid hormone on bone and an indirect effect of the hormone on growth hormone release and IGF-I action. Both thyroid hormone receptors alpha and beta are expressed in bone cells. To examine the role of thyroid hormone receptor beta on bone, the growth abnormalities in the human syndrome of resistance to thyroid hormone caused by mutations in the thyroid hormone receptor beta gene are reviewed. These mutant receptors reduce the tissue responsiveness to thyroid hormone, producing variable degrees of thyroid hormone deprivation in some tissues. With regard to bone, relative thyroid hormone deficiency caused by the mutant thyroid hormone receptor beta produces short stature and delayed bone growth. These observations indicate that an intact thyroid hormone receptor beta is required for normal bone development and growth.