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 is very specific in the cell type it targets.
B) It is a stimulant of cellular metabolism and targets all cells.
C) It does not require a second messenger to effect a response.
D) It causes positive feedback.

Question

Quizplus · Accepted Answer

Thyroxine, unlike most peptide hormones, is lipid-soluble and can cross the cell membrane to directly affect the cell's nucleus without the need for a second messenger.

Thyroxine Is a Peptide Hormone, but Its Mechanism Is Different