Which hormone is a steroid that binds to intracellular receptors to exert its effects?

Which hormone is a steroid that binds to intracellular receptors to exert its effects?

• A. Estradiol
• B. Epinephrine
• C. Growth hormone
• D. Follicle-stimulating hormone

Answer: (A)

Steroid hormones are lipid-soluble and cross the cell membrane to bind intracellular receptors that act as transcription factors. Estradiol fits this pattern: as an estrogen derived from cholesterol, it diffuses into cells and binds its receptor inside the cytoplasm or nucleus. The receptor–hormone complex then modulates gene expression, altering which proteins are made and leading to longer-lasting, genomic effects in target tissues. Epinephrine, growth hormone, and follicle-stimulating hormone are not steroids. Epinephrine is a water-soluble catecholamine that binds receptors on the cell surface to trigger rapid signaling cascades via second messengers. Growth hormone and FSH are peptide hormones that also act through cell-surface receptors, initiating signaling pathways rather than changing gene transcription directly through intracellular receptors.

Steroid hormones are lipid-soluble and cross the cell membrane to bind intracellular receptors that act as transcription factors. Estradiol fits this pattern: as an estrogen derived from cholesterol, it diffuses into cells and binds its receptor inside the cytoplasm or nucleus. The receptor–hormone complex then modulates gene expression, altering which proteins are made and leading to longer-lasting, genomic effects in target tissues.

Epinephrine, growth hormone, and follicle-stimulating hormone are not steroids. Epinephrine is a water-soluble catecholamine that binds receptors on the cell surface to trigger rapid signaling cascades via second messengers. Growth hormone and FSH are peptide hormones that also act through cell-surface receptors, initiating signaling pathways rather than changing gene transcription directly through intracellular receptors.