What is a key characteristic of steroid hormones?

The key characteristic of steroid hormones is their ability to alter gene transcription inside the nucleus. Steroid hormones are lipid-soluble molecules that can pass through the cell membrane and enter the target cells. Once inside, they typically bind to specific receptors in the cytoplasm or nucleus. This hormone-receptor complex then interacts with DNA, specifically at certain promoter regions, to initiate or suppress the transcription of specific genes. As a result, this process leads to changes in protein synthesis, which can affect physiological responses over a longer duration compared to other types of hormones.

The other options describe mechanisms that are more typical of peptide hormones or other types of signaling molecules. For instance, fast-acting responses through the circulatory system and triggering immediate nerve impulses pertain to non-steroid hormones that generally act more quickly by binding to receptors on the cell membrane and activating secondary messenger systems.