Answer: Diffusing across the plasma membrane and binding intracellular or nuclear receptors that alter gene transcription.
- A Diffusing across the plasma membrane and binding intracellular or nuclear receptors that alter gene transcription
- B Being actively transported into the cell by receptor-mediated endocytosis in general clinical practice as frequently documented
- C Binding a cell-surface receptor that activates a second messenger cascade without entering the cell in most observed cases
- D Opening ligand-gated ion channels directly on the plasma membrane under typical physiological conditions according to standard texts
Correct answer: A. Diffusing across the plasma membrane and binding intracellular or nuclear receptors that alter gene transcription
Explanation: Being lipophilic, steroid hormones cross the plasma membrane and bind intracellular/nuclear receptors, with the hormone-receptor complex regulating gene expression.
The hypothalamus releases hormones that direct the pituitary, which releases its own trophic hormone to a target gland; that gland's hormone output then feeds back (dashed lines) to suppress both the pituitary and hypothalamus once levels are sufficient - a self-correcting loop running the entire endocrine system.
Concept context
The endocrine glands, hormone classification and mechanism of action, and negative feedback regulation.