Site selectivity of osteoblast gene expression response to thyroid hormone localized by in situ hybridization

The effects of L-thyroxine-induced suppression of thyroid-stimulating hormone (TSH) of bone gene expression were analyzed by in situ hydbridization in male Sprague-Dawley rats. Supraphysiological doses of L-thyroxin in rats reduced femoral bone mineral density (BMD) without altering the BMD of the vertebrae. The absence of osteoblast-specific gene expression in vertebral osteoblast compared to femoral osteoblast was due to the inability of L-thyroxin in altering vertebral BMD.