Calcitriol, popularly known as the active form of vitamin D, is a hydrophobic hormone. Which of the following is most likely to be a correct statement about calcitrol signaling?
A) Calcitriol binds to a transporter to cross the membrane.
B) Calcitriol binds to plasma membrane receptors.
C) Calcitriol forms hormone-receptor complexes in the cytoplasm.
D) Calcitriol exerts its effects by stimulating an intracellular second messenger system.

Question

Quizplus · Accepted Answer

Calcitriol is a hydrophobic hormone that can freely pass through the plasma membrane. Once inside the cell, it binds to its intracellular receptor in the cytoplasm, forming a hormone-receptor complex. The complex then translocates into the nucleus and binds to specific DNA sequences, known as vitamin D response elements (VDREs), to modulate gene transcription. Therefore, option C is the correct statement about calcitriol signaling.

Calcitriol, Popularly Known as the Active Form of Vitamin D