Final answer:
Insulin is a non-steroid hormone that binds to receptors on the cell membrane, not intracellularly, unlike steroid hormones like estrogen, cortisol, and thyroxine. The correct answer is option b.
Step-by-step explanation:
The hormone that does not act by binding on intracellular or nuclear receptors is insulin. Unlike steroid hormones like estrogen, cortisol, and thyroxine, insulin is a non-steroid hormone made of amino acids. Instead of diffusing through the cell membrane to reach intracellular receptors, insulin binds to receptor proteins on the surface of the target cell's membrane. This interaction triggers a series of events within the cell, involving second messengers, which influence cellular processes.
Steroid hormones, on the other hand, are lipid-soluble and can diffuse directly through the plasma membrane to bind with intracellular receptors, either in the cytoplasm or nucleus, to regulate gene transcription by acting on DNA. Therefore, the correct option is (b) Insulin.