How do steroid hormones differ from peptide hormones in their mechanisms of action?

Steroid hormones are lipophilic molecules that can easily pass through cell membranes due to their hydrophobic nature. Once inside the target cell, they typically bind to specific intracellular receptors located in the cytoplasm or nucleus. This hormone-receptor complex then translocates to the nucleus, where it interacts with DNA to influence gene expression, leading to a change in protein synthesis. This mechanism allows steroid hormones to exert long-lasting effects on cellular functions, such as regulating metabolism, immune responses, and reproductive functions.

In contrast, peptide hormones, which are hydrophilic and cannot easily cross cell membranes, generally bind to receptors on the cell surface. This binding initiates a cascade of intracellular signaling pathways but does not directly influence gene expression in the same manner that steroid hormones do. Therefore, the key distinction lies in the ability of steroid hormones to affect gene expression by passing through the cell membrane, highlighting the unique mechanism of action they possess compared to other hormone types.