Here's how it works:
1. Testosterone is a steroid hormone, meaning it's lipid-soluble and can easily pass through the cell membrane.
2. Inside the cell, testosterone binds to an intracellular receptor called the androgen receptor (AR). This binding causes a conformational change in the AR, activating it.
3. The activated AR complex then translocates to the nucleus, where it interacts with DNA.
4. The AR binds to specific DNA sequences called hormone response elements (HREs). This binding can either activate or repress gene expression, depending on the specific HRE and the context of other regulatory proteins.
Therefore, by binding to an intracellular receptor, testosterone can directly influence the transcription of genes, leading to changes in protein production and ultimately, cellular function.
This is just one example, and many other steroid hormones, like estrogen and cortisol, use similar mechanisms to regulate gene expression.
