What distinguishes steroid hormones from peptide hormones?

• A. Steroid hormones are hydrophobic and can pass through cell membranes, while peptide hormones are hydrophilic and cannot.
• B. Steroid hormones bind to surface receptors, peptides enter the nucleus.
• C. Steroids are degraded before signaling, peptides are not.
• D. Steroid hormones are always produced in the pituitary.

Answer: (A)

The difference rests on the chemical nature of the hormones and how that shapes their signaling. Steroid hormones are hydrophobic and derived from cholesterol, so they can cross the cell membrane. Once inside, they typically bind to intracellular receptors and influence gene transcription, leading to slower, longer-lasting effects. Peptide hormones are hydrophilic and cannot cross the membrane; they bind to receptors on the cell surface and activate signaling cascades via second messengers, producing rapid responses.

This explains why the other ideas don’t fit: peptide hormones do not enter the nucleus to act directly, steroids aren’t degraded before signaling in the general sense (they act through their receptors), and steroids aren’t exclusively produced in the pituitary.