Steroid hormones and bone

Steroid hormones have an important impact on bone. The mechanism of steroid action on bone cells is through an interaction with specific receptor proteins in the target cells. Steroid receptors are a class of molecules that function as both signal transducers and transcription factors. The receptors each have similar functional domains that are responsible for discrete functions. The mechanism of receptor action is mediated by both genomic and nongenomic pathways. It is believed that in genomic pathway the steroid passes through the cell membrane by passive diffusion and binds to the receptor within the nucleus. Steroids have direct action on osteoblasts via receptor, and the effects of steroids on osteoclastic bone resorption are mediated through osteoblasts which release soluble factors by the action of hormone-receptor binding. However, in addition to indirect effects on osteoclasts, the question whether steroid hormones could exert direct action on osteoclasts as well has not to be answered and findings to date are controversial. It is not doubt that understanding the precise molecular mechanism of steroid action on bone resorption will develop new approaches for the diagnosis and treatment of disease associated with osteoclastic bone resorption.