At what point can terminal hair revert back to vellus hair?

Terminal hair, which is typically thicker, darker, and longer, can undergo significant changes under various conditions, particularly hormonal influence. However, once hair has fully transitioned to terminal hair, it does not revert back to vellus hair under normal circumstances.

The process that causes hair to become terminal, such as genetic factors and hormonal changes—especially increased androgens—entails a transformation that is not easily reversed. While factors like repeated waxing or consistent shaving can influence hair growth patterns and perhaps even the density of hair over time, they do not cause a complete transition back to vellus hair. Vellus hair is soft, fine, and lighter, often lacking pigmentation and a medulla, whereas terminal hair is significantly different in structure.

Hormonal treatments may affect hair growth and potentially lead to changes in hair characteristics, but they do not facilitate a transition from terminal back to vellus hair in the way suggested in the other options. Therefore, it is accurate to state that terminal hair, once developed, does not revert to vellus hair.