Which type of hormone can cross cell membranes and typically binds to intracellular receptors?

• A. Nonsteroid hormones
• B. Steroid hormones
• C. Amine hormones
• D. Peptide hormones

Answer: (B)

Lipid-soluble hormones cross cell membranes and act by intracellular receptors. Steroid hormones fit this pattern because they are lipid-soluble and diffuse through the plasma membrane into the cell. There they bind to receptors located in the cytoplasm or nucleus. The hormone–receptor complex then acts as a transcription factor, turning genes on or off and changing protein synthesis. This direct effect on gene expression explains why steroid hormones produce slower but longer-lasting actions compared to other hormones.

In contrast, nonsteroid hormones, amine hormones, and peptide hormones are typically hydrophilic and cannot easily cross the cell membrane. They bind to receptors on the cell surface and trigger signaling cascades inside the cell, leading to rapid responses that are usually shorter in duration.