What is a unique aspect of lipid hormone signaling compared to GPCRs and RTKs?

• A. Lipid hormones activate tyrosine kinase activity like RTKs.
• B. Lipid hormones require a second messenger system like GPCRs.
• C. Lipid hormones are always protein-based like GPCRs.
• D. Lipid hormones can diffuse through membranes to bind intracellularly, unlike GPCRs and RTKs.

Answer: (D)