View source for Steroid

=== Steroids and intracellular receptors  ===

[[Image:Nuclear Receptors.jpg|frame|643x367px|Nuclear Receptors.jpg]]

[[Steroids|Steroid hormones]] are&nbsp;lipids and so can&nbsp;enter the cell by simple diffusion across the [[Phospholipid bilayer|plasma membrane]]. The receptors for this hormone&nbsp;exist either in the cytoplasm or nucleus, which&nbsp;is where the&nbsp;hormone binds to them. When the&nbsp;hormone binds to&nbsp;the&nbsp;receptor, a&nbsp; series of events occurs: 

<br> 

*The receptor is activated due to a&nbsp;conformational changes in the [[Neurotransmitter|receptor]] induced by the binding hormone. This activation&nbsp;leads to the receptor being able to&nbsp;bind to&nbsp;[[DNA|DNA]]. 
*Activated receptors bind to the [[Transcription|DNA]] binding domain, which are short specific sequences of DNA which are located in promoters of hormone-responsive genes. 
*Transcription from those genes to which the receptor is bound is affected. Most commonly, receptor binding stimulates transcription.

The hormone-receptor complex at&nbsp;the ligand binding domain&nbsp;thus&nbsp;behaves as a [[Transcription factor|transcription factor]]. Due to steroid hormone's ability to diffuse freely through the lipid bilayer due to being hydrophobic they can have a long lasting effect on a target cell and their signal and remain active from hours - days <ref>1998, Hormones with Intracellular Receptors, http://www.vivo.colostate.edu/hbooks/pathphys/endocrine/moaction/intracell.html, 22.11.12</ref>. 

=== References  ===

<references /> 

<br>