| Hormones | Enzymes |
| 1. Hormones may be amino acid derivatives, peptides, proteins or steroids in nature. | 1. All enzymes are complex proteins. |
| 2. They have low molecular weight and often readily diffuse through cell membranes. | 2. They have very high molecular weight and are not diffusible. |
| 3. They are secreted by cells at one site and pass via blood to another site to act. | 3. They are secreted by cells and may act in the cells themselves or pass via ducts to act in some cavity in the body. |
| 4. They are used up in their regulatory action. | 4. They remain unaffected in the reaction they catalyze. |
| 5. They may act slowly or quickly. | 5. They act quickly. |
