Thyroxine is a peptide hormone, but its mechanism is different from other peptide hormones. Which of the following statements is True concerning this difference?
A) It causes positive feedback.
B) It does not require a second messenger to effect a response.
C) It is very specific in the cell type it targets.
D) It is a stimulant of cellular metabolism and targets all cells.

Question

Quizplus · Accepted Answer

Unlike other peptide hormones, thyroxine does not require a second messenger to effect a response. Instead, it enters the target cell and binds to specific receptors in the nucleus, where it directly alters gene transcription and protein synthesis. This is a characteristic of steroid hormones, which thyroxine closely resembles in its mechanism of action.

Thyroxine Is a Peptide Hormone, but Its Mechanism Is Different